Organbuilders and research: Two points of view

Francesco Ruffatti and Judit Angster

The following is a response to the article “Organbuilders and research: Another point of view,” by John M. Nolte (The Diapason, July 2010, pp. 20–21), which was itself in response to the article “Organbuilders and research: Two points of view,” by Francesco Ruffatti and Judit Angster (The Diapason, January 2010, pp. 24–27).

I found the article in the July issue (pages 20–21) written by my colleague John M. Nolte very interesting and informative. We are probably of the same age: I too have been involved in organbuilding for well over 40 years. Having said that, I should also say that I do not really believe that longevity in organbuilding practice is what counts the most: one can repeat the same mistakes for decades, and at the same time a bright young organbuilder can find innovative ways quickly. Experience plays a role, but it is the personal attitude that makes the real difference. In any case, we both seem to be curious enough to try to get to the bottom of organbuilding issues. For this reason, I have chosen to be involved in research, and have been lucky enough to find the connection, during the last ten years, with the very respected and reputable Fraunhofer Institut für Bauphysik in Stuttgart.
Having practiced both open-toe and closed-toe voicing for quite some time, going through a variety of organbuilding “trends,” and having come in the end to some empirical conclusions, I was always curious to find out why I was considering one method better than the other for certain applications. Specifically, I have no problem in stating that under “average conditions”—let us say at around 3 inches of wind—I obtain better results with open-toe voicing on principals and flutes, and better results with closed-toe voicing on strings. If I have to raise the pressure further, to increase the sound energy at its source (sometimes you have to, especially in poor acoustics), I find it easier to control principals and flutes if I voice them with open toes. “Better results” are always subjective, of course, and personal taste plays an important role, as I stated in my original article.
Dr. Angster, Dr. Miklos, and other scientists—all top names in organ acoustics—have explained to me not only the Bernoulli formula, which in the end is not so complicated, but a number of other theories and esoteric formulas. I tend to be “practical,” like many organbuilders, and will not deny having been taken by surprise in seeing how variable the scenario can be in toe wind pressure values, after boring holes and applying pressure sensors to the sides of the pipe feet.
In a perfect world, one could put each stop on its own wind pressure in order to compensate for open or closed toe, in order to obtain, as Mr. Nolte suggests, equal wind pressure at the languid, which is not an easy thing to actually measure, unless you bore holes at the toes as we did during the research. In the real world, when you are voicing a chest of pipes in a Swell division containing principals, flutes, strings and reeds, then you have fewer choices. This is where a practical comparison of the two methods, given equal windchest pressure, becomes meaningful. While I respect Mr. Nolte’s idea, the choice that we made in establishing a research procedure was different, as Dr. Judit Angster explains well in her section of this article. I will never say that “my way is the only way,” and I would ask for the benefit of the doubt from others as well.
The issue of the so-called “wind noise” is, in my opinion, the key to, not a side aspect of, the whole matter. I have been told that what causes turbulence—and noise as one of the results—is a sudden restriction in the air flow. In other words, if we restrict the maximum flow from the diameter of the windchest hole, by closing the pipe toe, turbulent conditions are created. The “open toe” is so open that it looks exaggerated: this is not done to make sure that enough wind gets into the pipe, but rather to avoid as much as possible a restriction in the flow. The shape of the pipe tip may have some influence in the noise, but the real issue does not change. Actually, by looking at photo 2 of Mr. Nolte’s article, it seems to me that the hole with the countersink, which he refers to as “quiet toe-hole,” seems to direct the flow inwards, towards the center of the flow, thus potentially creating the opposite of what a “diffuser” would do. A diffuser is a device that is aimed at reducing turbulence from flow restrictions. On this matter, we have some interesting results from previous research on wind supply.
If noise is created, at equal windchest pressure conditions, Mr. Nolte agrees with me that by reducing the wind flow at the lower lip, which is the only way to control volume in an open-toe flue pipe, the wind noise is reduced as well. I take this as a strong indication of the validity of the open-toe system for the “classical stops,” where it is not as desirable to nick the languids. For the strings, the matter is different, and the need to reduce the pressure in the toe is linked to the need for keeping the mouth cutup to reasonable levels in spite of the smaller relative diameter of the pipes, to preserve clarity. Nicking is, for these pipes, a normal condition (except in rare occasions—for example, the “Violetta” by Callido).
Voicing is very personal, and tastes are different. I am sure that Mr. Nolte does a fine job with voicing, given his experience, regardless of the method. As to wooden pipes, I am happy to hear that he has done research on this aspect as well. We are doing the same, possibly with some different objectives: not only to find better transitions, but also, for example, to speed up the speech on very large 16′ open wood pipes. I will read Mr. Nolte’s reprint when it becomes available, as well as the description of his all-wood practice organ. I sincerely wish him the best of luck in his efforts. After all, we are all in the same boat, and all for the same reason: we all love the work that we do.
—Francesco Ruffatti

In my contribution to the article, I tried to release information about our current research project on organ pipe voicing and scaling. Within this context, I mentioned our investigation on open and controlled toe voicing, as one example of the ongoing research. Unfortunately, the goal of this experiment was not formulated clearly; therefore I have to accept Mr. Nolte’s ironic criticism as justified.
Certainly, the group of scientists and I, who have been working together for several years on organ pipe research, know very well that “the velocity of air at the flue is determined by the pressure in the foot of the pipe just below the languid” and that “in every case, the voicing pressure is lower than the windchest pressure.” But we also know that not only “the velocity at the flue” “matters for pipe speech,” as Mr. Nolte states. A more important factor for the speech is the velocity at the upper lip, and that velocity depends also on other parameters. The air jet emerging from the flue must obey the physical law of momentum conservation; therefore its maximal velocity V at a distance y from the flue can be given as V(y)≈UB(d/y)1/2, where UB is the Bernoulli-velocity and d is the width of the flue. The air jet is directed usually slightly outside; therefore it hits the upper lip at a velocity that is lower than its maximal velocity. The direction of the jet depends on the relative position of the languid and lower lip. The task of the voicer is to find the optimal adjustment of the mouth area to ensure the required loudness and speech of the pipe. From the standpoint of science, the voicer adjusts only two physical quantities: the air volume through the flue and the velocity at the upper lip. In the case of a constant windchest pressure, the air volume is adjusted for closed-toe pipes both at the toe and at the flue; in the case of open-toe pipes, it is adjusted only by means of regulating the flue width. The velocity at the upper lip depends on several parameters: the Bernoulli-velocity (which depends on the foot pressure), the width of the flue, the cutup, the positions of lower lip, languid, and upper lip, etc. The essence of the art of voicing is to find the optimal adjustment of these parameters only by listening to the sound.
The velocity profile of the air jet depends also on other parameters like the profile and angle of the languid, nicking, etc. In order to get more information about the properties of the air jet, the free outflow from the flue of metal organ pipes and edge tone generation at the upper lip was the subject of a three-year Ph.D. project at the Fraunhofer IBP, which will be completed this year.
If two identical pipes are placed on the same windchest, one with open toe and the other with closed toe, it is possible to get the same velocities at the upper lips by reducing the flue width of the pipe with open toe. This opportunity has led us to the idea of voicing the two pipes on the same windchest pressure, to the same volume of sound. Thus the goal of the investigation was to voice the pipe with open toe and the pipe with closed toe to the same loudness and then compare their steady spectra and attack transients. Preliminary results of this investigation were presented in our article.
For us scientists, it was astonishing to witness how similar the achieved sound was from both types of pipes. Steady spectra and attack transients, measured by our special method, were very similar. The only easily measurable difference was the lower wind noise level on the pipe voiced with open toe at 70 mm water column pressure.
In a closed-toe pipe, the foot pressure may be significantly lower than the pressure in the groove. This pressure difference accelerates the flow through the smaller cross-section of the foot hole. The cross-section of the foot will then suddenly become much wider and the flow velocity will decelerate. This acceleration/deceleration process can generate noise and pressure fluctuations. With open toe, neither pressure difference nor sudden velocity changes occur. As the measurement results in Figure 5 of our original article show, the wind noise level in the pipe sound is lower in the case of voicing with an open pipe foot.
The common research with voicers has proven that good speech and steady sound can be achieved by both voicing methods. The voicer should decide which method he prefers; this is a question of taste and experience, not of science.
—Judit Angster

John M. Nolte

John M. Nolte has been in organ building for more than 40 years. In 1986 he founded his own company, which has grown to a staff of five, including his sons Benjamin and Jeremy. The firm has an international reputation for quality wood pipes. They have supplied voiced and unvoiced pipes to many of the best American organbuilders, and recently completed a commission for all of the wood pipes in the new Nicholson organ at Llandaff Cathedral. Nolte has been active in the American Institute of Organbuilders for the past ten years, and has shared technical information with that organization with a Journal of American Organbuilding article, convention lecture, and mid-year seminar on various aspects of wood pipe scaling, production, and voicing. The firm is currently focusing on a highly refined mechanical action.

The January 2010 issue of The Diapason featured an article by Judit Angster and Francesco Ruffatti on organbuilders and research.1 This kind of work is very necessary and useful, and it can generate profitable discussion that leads to a better and broader understanding of the pipe organ. The research reported in January is far from complete, but it is a very good discussion starter. Several things in the article struck a chord with me, and I will elaborate on two of them. In this article I will discuss the open-toe versus closed-toe question on the basis of a little technical background that goes back to Daniel Bernoulli, an 18th-century Swiss scientist. This will be followed by a reprint of my article, “Scaling Pipes in Wood,” originally published in the Journal of American Organbuilding in March 2001.
The question of open-toe versus closed-toe requires an understanding of what organ wind pressure is with respect to voicing. There is a big difference between windchest pressure and voicing pressure. Windchest pressure is the pressure present at the toe of the pipe when the valve is opened. Voicing pressure is the pressure at the languid. In every case, voicing pressure is lower than windchest pressure. When we say an organ is on 5 inches wind pressure, measured in the chest, all we know about voicing pressure is that it is less than 5 inches—it could be 2 inches or less. What happens in the foot of the pipe is the key.
In the research article, one measurement that was taken was the wind pressure in the foot of the pipe. The author states, “To everyone’s surprise, it was noted that the wind pressure inside the pipe foot in open-toe pipes showed an average pressure drop of 10% or less from the original pressure inside the windchest, while in the closed-toe pipes, even though these were still fairly open, the pressure drop was about 40 to 50%.”2 I was surprised that a group of voicers and physicists was surprised. This is exactly what one should expect. Let’s look at what happens in the foot of the pipe. See Figure 1.
When the organist plays the note, air enters the foot of the pipe through the toe, and it exits the foot of the pipe through the flue. If the pipe is well made, and the toe is seated properly in the chest, all of the air that enters the toe leaves through the flue. When the chest pressure is higher, the air coming out of the pipe hole travels faster. When the pressure is lower, the air travels slower. The size of the hole does not affect the speed of the air—it just controls the volume of air that comes out of the chest. If the flue is completely closed so the air has nowhere to go, when the valve is open the pressure in the foot will rise until it is equal to the pressure in the chest. If we open the flue, air will escape from the foot, and the toe hole will replace it as fast as it can. In every case the pressure in the foot will be lower than the pressure in the chest. Because the volume of air leaving the pipe at the flue is the same as the volume of air entering at the toe, we can use variations of Bernoulli’s equation to predict what the difference in chest pressure and foot pressure will be. The rule is that the pressure drops at the toe and the flue vary inversely with the squares of their areas. Here is the formula:

(Atoe)2 = ΔPflue
(Aflue)2 ΔPtoe

where A is the area of the toe or flue, and ΔP is the pressure drop at the toe or flue.
Let’s illustrate this with a chart. If the original chest pressure is 100mm, then the area of the toe compared to the area of the flue will give these results for the pressure in the foot:

Atoe Aflue Foot Pressure
1 2 20mm
1 1 50mm
2 1 80mm
9.95 1 99mm

Notice that when the area of the toe opening and the area of the flue are the same, half of the chest pressure is lost in the toe, and half is lost when the air exits the flue to the atmosphere. When the toe opening is smaller than the flue, the pressure in the foot is even less than half of chest pressure. We have seen examples of pipes voiced on 10″ wind pressure that were actually speaking on 2″ wind pressure. For flue pipes, wind pressures of 8–10″ are found at the languid of fairground organs designed to be played outdoors and heard up to a quarter mile away. Rarely do indoor pipes receive pressures over 4″ at the languid. When the toe is larger than the flue, more than half of the chest pressure is present in the foot of the pipe. When the ratio is about 10:1, the toe is fully open and 99% of chest pressure is present in the toe.
For many years the American Institute of Organbuilders has recommended that in good flue voicing we aim for a toe that is twice the area of the flue. Notice from the chart that this yields 80% of chest pressure in the toe. This allows the voicer a little latitude to make the pipe louder or quieter by regulating the toe more or less open.
Why the emphasis on the pressure in the foot? Air passes through the flue to the upper lip where an oscillation develops that creates the standing wave in the body of the pipe. What matters for pipe speech is the velocity of the air at the flue, and that velocity is determined by the pressure in the foot of the pipe just below the languid. The blower pressure, the pressure in the chest, and the pressure at the bottom of the ocean are all irrelevant.
With this technical information in mind, I really must question the experiments that were supposed to determine whether or not there is a difference between closed-toe and open-toe voicing. The experiments referred to in the article state that windchest pressure was constant, and that pressure in the foot was twice as much for the open-toe compared to the closed-toe. Then both pipes were voiced to match loudness. This proves nothing about the difference between open-toe and closed-toe voicing.
If I voice a pipe with an open toe on 70mm wind pressure, and then voice a pipe with an open toe on 35mm wind pressure, and I make the two pipes equally loud, will there be a difference in tonality? Of course there will be. The pipe voiced on the higher pressure will drive the upper harmonics more in relation to the fundamental, and the tone will be brighter. That is exactly what the chart in Figure 5 in the article illustrates. The only difference is that the researchers achieved a pressure in the foot of about 35mm by closing the toe, instead of opening the toe and setting windchest pressure at 35mm.
If I want to compare open-toe voicing to closed-toe voicing, the pressure in the foot must be the same, not the pressure in the windchest. If we use the toe-to-flue ratio of 2:1, that means that to achieve the same tonality between the two voicing methods, the chest pressure for the closed toe must be 25% higher. If I voice an open-toe pipe on 80mm windchest pressure, I must voice the comparable closed-toe pipe on 100mm windchest pressure. The cut-up, the size of the flue, and the treatment of the languid should be the same.
When organs started to use tubular pneumatic and electro-pneumatic actions, these early actions required windchest pressures of 4″ to 6″ to operate properly. When these new chests were used to rebuild older organs that were voiced on lower pressures with open or nearly open toes, the old pipes had to be revoiced to the higher windchest pressures. Frequently, all the voicers did with the old pipes was to close the toes until the pressure in the foot was lowered to where it had been originally. This method is fast, and if the pipes were going back into the same room, the original voicing and regulation was already correct.
In the last few years we happened upon a large supply of treble pipes that were well made and voiced with open toes on low pressure, around 65mm (21⁄2″). We have used them to replace inferior trebles in a number of sets of pipes on several different, but higher, pressures. Closing the toes was all that was necessary, unless the pipes needed to be made significantly louder.
To do a meaningful comparison between open-toe voicing and closed-toe voicing, several identical pipes should be voiced to match as perfectly as possible with open toes. Then raise the windchest pressure for one of them and see if closing the toes will bring back the match. It will.
The researchers also noted another difference:

Under equal conditions, the ‘wind noise,’ a natural component of the pipe sound that the voicer normally tends to reduce or eliminate, was by far more noticeable in closed toe pipes. This is not at all an irrelevant difference: in practical terms, it means that pipes voiced with closed or partially opened toes will require a heavier presence of ‘nicks’ at the languids in order to control wind noise, and this in turn will determine significant modifications to the structure of their sound.3

There are several distinct ways wind noise can be generated in a pipe with closed toes, and the treatment must address the problem. Nicking is seldom the only solution, and rarely is it the best solution for eliminating wind noise.
At the toe, if chest pressure is quite high, the velocity of the air through the toe can create turbulence and, consequently, noise. Turbulence is exacerbated when friction in the toe opening slows down the air at the boundary of the hole, while the air towards the middle of the hole is unimpeded. The solution is to carefully countersink the toe hole so that the smallest part of the hole comes to a point in the cross-section. See the photos for examples of a noisy and a quiet toe. The closed toe pictured in the research article has not been properly treated to keep it as quiet as possible.
At the flue, noise is generated when the flue is overly large. This happens for different reasons. When the chest pressure or foot pressure is too low, the flue must be opened more to get enough volume of air to produce a loud enough sound. This can happen with either open or closed toes. When the pressure in the foot is too high, opening the flue will lower the foot pressure, but it also creates a wider air stream than necessary to create the musical note, so some of the air generates noise, not tone. Large flues are also sometimes used to compensate for upper lips that are too thick. Once again, excessive amounts of air traveling through the flue create unwanted and unnecessary noise. A thinner lip and smaller flue will eliminate the problem.
When the area of the toe is relatively small compared to the flue, the velocity of the air entering the toe is substantially higher than the velocity of the air exiting the flue. As the air in the foot slows down, the degree to which it has to slow down will create turbulent conditions in the foot of the pipe, which generate noise both in the foot and at the flue. Some voicers use steel wool or other devices in the foot itself to overcome this.
Nicking can be used to control wind noise in all of these circumstances, and if the tonal quality resulting from the nicking is what one wants, so be it. If, instead, we want a tone more like what is achieved without nicking in open-toe voicing, attention to detail can achieve this quite easily.
The 2:1 relationship of toe area to flue area, along with the correct windchest pressure, will overcome these problems. A ratio of 1:1 can be used with good results if the voicer is very attentive to detail. When the toe becomes smaller than the flue, trouble is not far behind. The use of partially closed toes to regulate pipe speech can provide results equal in virtually every respect to what can be achieved with open toes. In order to accomplish this, it is necessary for the windchest pressure to be higher than it would be for open-toe voicing so that the pressure in the pipe foot is ideal. Raising the chest pressure too high can cause wind noise problems, but these can be controlled by keeping the windchest pressures from being excessive. So much for my contribution to this part of the discussion.
The researchers also mentioned investigations into transitions between stopped and open pipes, or between wood and metal pipes within the same rank. My research on wood pipes will be presented in the reprint of my March 2001 article, “Scaling Pipes in Wood.” The research for this article was based on years of making reproductions of wood pipes for antique orchestrions, and a study of historic wood pipe scaling, notably the Compenius organ of 1610. On the practical side, this led to a commission for an all-wood practice organ, which also had strict action requirements. This organ will be featured in a future article.

 

Fratelli Ruffatti, Padua, Italy
Wesley Chapel, Elkton, Maryland

From the builder
Fratelli Ruffatti is mostly known in the United States for building large four- and five-manual instruments with electric action. Two five-manual organs have been completed in the past 15 months, and two four-manual organs are currently being manufactured in the Ruffatti workshop. Few people, however, know that the majority of instruments that the firm produces outside of the United States are of mechanical action.
In tune with the trends and ideas that were coming from across the Alps at the beginning of the 1960s, Ruffatti was among the first in Italy to restore the tradition of building pipe organs with suspended mechanical action. One of the most famous of these instruments is in northern Italy, installed in 1970 in the parish church of the small medieval city of Noale. It is not a huge instrument, numbering 27 stops and 35 ranks of pipes over two manuals, but it became quickly famous from the beginning as the concert instrument for the first Italian competition of young organists. It is still today the centerpiece of a quite famous concert series, involving big names among international organists.
Ruffatti is here presenting to the American organ community an instrument that is quite small, but of large significance. Everyone knows that ancient Italian organs were, for the most part, of small size—one manual, with a limited number of stops—but quite musical and versatile. Since our predecessors could not depend upon a large number of voices to produce variety, they refined their voicing techniques to the point that every sound could be combined with every other to produce the most versatility even within a very limited number of stops. This is the tradition that Italian organbuilders come from and that constitutes the inspiration for Fratelli Ruffatti even today, whether it may be applied to very large or, even more importantly, to small instruments.
The organ manufactured for Wesley Chapel of Elk Neck is a good example of how a very small instrument can be pleasing and effective in spite of its very limited size. With only one manual and a total of six stops, including the Pedal, it is difficult to imagine any kind of versatility at all. However, a few special ingredients grant this instrument a real flexibility: the divided stops, the composition of the Mixture and, above all, the voicing techniques.
Splitting the stops in bass and treble is an old practice in ancient organs, as we all know, and it allows the organist to create two different tonal “platforms” within the same manual. In this case, both the Principal and the Spitzflöte are divided between C and C# in the middle of the keyboard, thus increasing the number of possible combinations. The Mixture, whose composition is shown below, has been designed in such a way that no “double pitches” occur when combined with the 2′ Fifteenth. The Fifteenth and Mixture are conceived as an effective three-rank Mixture when pulled together, but at the same time the Mixture can also be independently used in a “mezzo ripieno” combination without the Fifteenth, creating a very interesting tonal color.
Although English names have been chosen for the stops, as a sign of respect for the users, a number of tonal features are present that link this instrument in many different ways to the classical Italian tradition.
The Principal pipes, both internal and in the façade, are without “ears,” as in the classical Principale. The low octave of the stop is made of stopped mahogany pipes, housed against the ceiling inside the case. They are connected to the windchest through a complicated series of metal windways. A stopped wooden low octave for the Principale is a common feature of the Positivo Italian organs of the 17th and 18th centuries, and effective ways have been refined over the centuries—through proper scaling and voicing—to make the bridge between wood and metal remarkably smooth.
The Octave is of slightly smaller scale, or relative diameter, than the Principal, as found in many historical organs of northern Italy, as are the Fifteenth and the subsequent Mixture ranks.
The 4′ Spitzflöte is an almost identical replica of the Flauto in Ottava, a stop of rare singing quality used by Gaetano Callido1 in his instruments.
With the primary purpose of providing a good foundation, especially considering the rather dry acoustical environment of Wesley Chapel, an independent, real 16′ Bourdon has been provided for the Pedal, with pipes made of African mahogany, which are located behind the organ case.
The voicing technique is probably the element of highest significance. At the lowest wind pressure allowed by the acoustical conditions of the room (65 mm at the water column, or slightly over 21⁄2 inches), all pipes have been voiced with completely open toe and a minimum number of barely visible nicks at the languids. The result is a very pleasing, singing tone without excessive chiff or unnecessary non-harmonic overtones. This constitutes the foundation for a successful blending of the stops as well as for the creation of successful, pleasing solo voices. The pitch is 440 Hz at 20° Celsius and the temperament is equal.
Architecturally, the organ case has been designed to fit in the historical surroundings of Wesley Chapel. Although inspired both mechanically and aesthetically by the ancient Positivo organs, it must not be defined as a copy: its design is definitely a new, original creation. It features a façade composed of 22 pipes divided in two symmetrical sections. Each is topped by a hand-carved panel designed to add beauty to the ensemble while at the same time allowing for maximum sound egress. Two hand-carved wooden elements at the sides provide the necessary continuity between the top and the lower part of the case.
The casework is made completely from solid African mahogany. The keyboard features bone naturals with carved key fronts, and natural ebony sharps with bone inlays. The key cheeks are inlaid with thin strips of bone. The draw knobs are of ebony, with maple insets. The concave and parallel pedalboard (BDO measurements) is made of oak, with the sharps topped by ebony.
The mechanical action is suspended. The rollerboards are made from solid aluminum rollers with wooden arms.
The task of designing and manufacturing an instrument within such a small space has not been an easy one. In spite of this, every part is easily accessible for maintenance and ordinary tuning. The layout of pipes over the slider windchest in particular has been carefully designed to allow favorable conditions for the radiation of sound from all pipes.
—Francesco Ruffatti

Notes
1. Gaetano Callido was the most famous Venetian organbuilder of the 18th century. A pupil of Pietro Nacchini, he built over 430 organs in his lifetime, many of which are still preserved.
2. The basic principle of the open toe voicing technique is that of leaving the pipe toe completely open and regulating the sound volume by reducing the opening at the flue, or lower lip of the mouth. By operating this way several advantages are achieved, among which are a less turbulent air supply through the pipe foot and a more focused wind column at the mouth. These features are effective in reducing the “mouth noise” or “air noise” and, consequently, in reducing the need for languid nicking, a practice that can alter the natural timbre and that tends to reduce the development of upper partials in the sound spectrum.

From the organist
Several years back Glenn Arrants inquired: if he purchased an organ, would I play it?—and fortunately I said yes. He then informed me this would be no ordinary organ, but a pipe organ to be built in Italy. Through the months ahead, Glenn kept me informed of the progress.
The anticipation increased over the two and a half-year wait for the organ to be built. Finally we received word it would be delivered to the chapel on July 3, 2007. I was so excited about the opportunity to see this process firsthand, that I took off from work to be there to take photos and witness the arrival.
Spread throughout the chapel were all of the pieces that would be assembled into a pipe organ—in two weeks! I thought I understood the complexity of the pipe organ until I witnessed this firsthand. Imagine my excitement to hear that I would be playing the organ the first time that Sunday morning, although the pedals were not completed—the sound filling the sanctuary that morning was just a sweet taste of what was to come the following week when the instrument was complete.
There was concern that a pipe organ would overpower the small sanctuary and the congregation, but this is not the case. The sanctuary is filled with wonderful music, and the congregation’s voices are supported beautifully. Even with full organ, there is no vibration anywhere in the 177-year old chapel.
To be the first organist of the Wesley Chapel Fratelli Ruffatti pipe organ is indeed an honor, and a once in a lifetime opportunity. One cannot help but think of the dedicated craftsmen who built the organ, all the attention to detail, and the beautiful voices of the pipes. It gives me great joy to be able to sit down and play this organ, so much so that what seem like minutes in time are actually hours of enjoyment—this fine instrument will serve the congregation and community of Elk Neck for generations to come.
—Alice Moore

From the dedication recitalist
It was a great pleasure to prepare a program for the dedication of the new Ruffatti organ for Wesley Chapel of Elk Neck. It turned out to be much less of challenge to prepare for a “small organ” than one might have suspected. The organ is well capable of playing standard literature, Bach and Telemann, and there is, in fact, wonderful variety to be had in various combinations of the voices. Most surprising was the excellent way the organ could be adapted to the modern works of Michael Burkhardt and Donald Johns in hymn-based partitas. Equally important, the gentle and very artistic voicing of this instrument allows it to lead congregational song with all the color and emotion one could ask for in an instrument of larger design. The divided stops are an ideal way to get “more organ” than the package seems to contain. Bravo Fratelli Ruffatti and congratulations to Wesley Chapel of Elk Neck.
–Donald McFarland

A brief history of Wesley Chapel of Elk Neck, Elkton, Maryland
Elkton, Maryland, a city of some 13,000 people, sits on Chesapeake Bay near the Delaware border. It dates from the 1700s and was a strategic crossroads during the Revolutionary War. Washington and Lafayette passed through it frequently, and it is very near the spot where the British landed for their march on Philadelphia. The Wesley Methodist Society formed its congregation there in 1797 and, in 1830, the parcel of land was bought “for and in consideration of the sum five dollars current money of Maryland,” and the Reverend William Ryder laid the cornerstone of a new building in which to hold the society’s services. Handhewn beams formed the 25′ x 30′ single-room chapel on a fieldstone foundation. The little building has several features that make it a particularly important structure architecturally, including a perfect half-circle arched ceiling, and varying-width clapboards that hide its vertical plank construction. Wesley Chapel seats about 50, and is one of the oldest rural chapels still in use in the area.
Glenn Arrants remembers how his mother served as church organist for almost 50 years. She played on an early 20th-century Möller organ, which took up considerable space in the tiny building. In the mid-1990s, the chapel went through a complete restoration and the Möller, which was then beyond repair, was replaced with a restored Estey reed organ. Church members missed the sound of a pipe organ, however, and, in 2005, set in motion plans to acquire an instrument specially built for the chapel. Because of the design work, the quality of construction, and the reputation of the company, Wesley Chapel chose Fratelli Ruffatti, distinguished pipe organ builders of Padua, Italy, to build its new instrument.

 

MANUAL—unenclosed, 56 notes (C–G)
8′ Principal Bass 25 pipes mahogany + 95% façade + 70% interior
8′ Principal Treble 31 pipes 95% façade + 70% interior
4′ Octave 56 pipes 70%
4′ Spitzflöte Bass 17 pipes 30% 1–8 common bass with Octave
4′ Spitzflöte Treble 31 pipes 30%
2′ Fifteenth 56 pipes 70%
II Mixture 11⁄3′–1′ 112 pipes 70%

PEDAL—unenclosed, 27 notes (C–D)
16′ Bourdon 27 pipes mahogany

7 ranks, 355 pipes
% = percentage of tin in tin-lead alloy

Composition of the Mixture II by itself
1–36 11⁄3′ 1′
37–48 22⁄3′ 11⁄3′
49–56 4′ 22⁄3′

Composition of the Mixture II together with the Fifteenth 2′
1–36 2′ 11⁄3′ 1’
37–48 22⁄3′ 2′ 11⁄3′
49–56 4′ 22⁄3′ 2′

James W. Toevs

Jim Toevs has a doctorate in nuclear astrophysics. While a professor at Hope College, he taught and consulted in acoustics. A musician, for 20 years he was the principal trumpet in the Los Alamos (NM) Symphony Orchestra and has sung in and directed church choirs.

Introduction1
With the installation and voicing of the wonderful new Fisk Opus 133 tracker organ in the First Presbyterian Church of Santa Fe, New Mexico, a number of interesting effects and impacts of Santa Fe’s thin air became apparent. This article will note the major observations and describe the physical acoustics related to organ pipe function at high altitude.
Santa Fe is located at the foot of the southern Sangre de Cristo mountains at an altitude of about 7,000 feet above sea level. In fact, the altitude at the church is 2,127 meters or 6,978 feet. At this altitude, both the atmospheric pressure and density of air are reduced to about 77% of their values at sea level. This difference in pressure corresponds to about 92 inches of water. Considering that most organs operate with a wind pressure of 2 to 4 inches (water column), this difference is quite significant. It is not surprising that organ operation is impacted by this difference; perhaps what is surprising is that the impact is not greater. The fine people of C. B. Fisk dealt with these differences with little difficulty.
Parameters in which high altitude might impact pipe organ performance include:
• Pipe intonation—essentially no effect;
• Windchest blower requirements—observed significant effect;
• Tone production: pre-voicing and voicing—observed significant effect;
• Sensitivity to windchest pressure—observed significant effect;
• Sanctuary acoustics—small but real effect.

Pipe intonation
The impact of altitude on the basic intonation of the organ pipes themselves is minimal. The frequency at which a pipe sounds (fundamental) is based on the length of the pipe and the speed of sound. The length, of course, does not depend on altitude, and fortunately neither does the speed of sound because the ratio of the pressure to density remains the same so long as the temperature is fixed. Basic intonation is therefore not affected by altitude.

Windchest blower requirements
The relationship between blower output (cubic feet per minute, or CFM) and desired windchest pressure (usually measured in equivalent inches of water column supported above the ambient pressure) is given by Bernoulli’s equation. This is perhaps the most fundamental law of fluid flow and basically is just a statement of the conservation of energy. Because density also decreases with altitude, a higher blower capacity will be required in high altitude installations than at sea level in order to obtain the same windchest pressure used at sea level. Using a higher output blower has become standard practice for high altitude installations.

Tone production: pre-voicing and voicing
As Mitchell and Broome have pointed out,2 windchest pressure must compensate for altitude differences when pre-voicing will be performed in a shop that is at a different altitude than the location at which the organ will be installed and receive final voicing. In both flue and reed pipes, the velocity has a direct impact on tuning and sound quality, and it is clearly desirable to produce the same pipe velocities during both pre-voicing and voicing. Once again from Bernoulli’s equation, since the density of air is greater at sea level than at high altitude, a higher windchest pressure must be used at sea level to produce the same velocities in the shop as in the installation. The desired shop windchest pressure is found by multiplying the desired windchest pressure at altitude by the inverse ratio of the atmospheric pressures at the two locations. This is the formula described by Mitchell and Broome.
Pressures of 3 inches and 4 inches were required for Opus 133, and the inverse pressure ratio between Santa Fe and sea level is 1/0.77 = 1.3. Therefore, pre-voicing in the Fisk Gloucester shop used pressures of 3.9 inches and 5.2 inches (water column).

Sensitivity to windchest pressure
During the final stages of voicing in Santa Fe, Fisk Opus 133 was performing very well, but suddenly developed significant intonation and sound quality problems when the HVAC (heat, ventilation, and air conditioning) system for the sanctuary switched between its two modes of operation. The change resulted in an increase of windchest pressure from 3 inches to 3¼ inches (water column). At sea level a change of ¼ inch could be accommodated without greatly impacting organ tuning and voicing, but in Santa Fe such was not the case. This sensitivity was not anticipated, but can be understood through an examination of tone production in organ pipes. In both flue and reed pipes steady energy is supplied through air streams produced by the windchest pressure, and a complex mechanism converts this energy into oscillating energy (sound).

Flue Pipes
In both a tin whistle and in flue pipes, production of oscillation, that is, tone, is through “edge tone generation.” The edge tone frequency depends strongly on air velocity through the windway, and must resonate with one of the natural modes (frequencies) of the pipe; the fundamental mode is always chosen. However, a small change in frequency of the edge tone can pull the edge-tone-pipe system away from the desired intonation. A small change in windchest pressure at altitude will result in a larger change in velocity (and therefore in pitch) than at sea level, due to the reduced density of air at altitude.

Reed pipes
In a reed pipe, air is supplied to the boot from the windchest at a pressure greater than the pressure in the resonator. This causes air to flow under the reed (tongue) into the resonator. Oscillation and therefore tone generation occur when very specific relationships are met among the variables and the stiffness of the reed. Both the stiffness and the oscillating length of the reed are set by the tuning wire.
The effect of a small change in windchest pressure on the frequency of a reed pipe is also greater than it is at sea level. Furthermore, the operating point of the reed, that is, the zero point of its oscillation, moves closer to the shallot as windchest pressure is increased. This may sharpen the onset of each cycle of the oscillation, increasing high frequency content, and, if close enough to the shallot, cause the flow under the reed to become turbulent. Both effects can alter the sound quality of the reed pipe.
To summarize this discussion, for both reed and flue pipes the sensitivity to small changes in windchest pressure is greater at altitude than at sea level, as the Fisk personnel discovered. The solution to this problem for Opus 133 was to gain a better understanding of the Santa Fe FPC sanctuary HVAC system and take appropriate steps to minimize the windchest pressure difference between the two operating modes. Figure 1 is a schematic of the system. The two modes of operation are as follows:
• Recycle mode: Air flows from the blower room to the sanctuary and is returned through the bellows room to the blower room. Valve R is open and Valve FA is closed down to 15%.
• Outside air mode: Outside air is brought in to the blower room and distributed to the sanctuary, and exits through the roof when the sanctuary pressure rises above that of the outside. The recycle valve is closed and the fresh air valve is 70% open.
Cost and environment are the two reasons for two modes of HVAC operation. During winter when outside air is well below the desired ambient temperature in the sanctuary, the air exchange is limited to the 15% required by code for healthy fresh air in the sanctuary (corresponding to the 15% setting of the fresh air valve). A larger percentage of fresh air would require more preheating, increasing gas costs. During summer when outside air is warmer than that desired for the sanctuary, a larger fresh air fraction would increase electric costs for cooling. On the other hand, during spring and fall, when some cooling is needed and outside air is marginally cooler than the desired sanctuary temperature, an increased recycle fraction saves cooling costs. Of course, environmental concerns track with increased gas and electric costs.
Organ pressure is supplied by the small blower in the bellows room and regulated by the bellows. It was found with a simple manometer (U-shaped tube with water) that the organ pressure during the recycle mode was 3 inches of water (that is, water in the manometer rose 3 inches), and in the outside air mode, the organ pressure was 3¼ inches (water column). The ¼-inch change significantly impacted tuning and sound quality. The reason for the ¼-inch change was that the recycle mode involved a great amount of air flow in the return ducts through the bellows room to the blower room, creating a pressure drop of ¼ inch in the return ducts. In this mode, then, the bellows regulating system had to supply 3¼ inches of pressure in order to yield the desired 3 inches of windchest pressure.
When the recycle valve closed to change to the fresh air mode of operation, the only flow in the return duct from the sanctuary to the bellows room was the much smaller flow used by the organ itself. Therefore, there was no loss in that section of duct, and the bellows room was essentially at the same pressure as the sanctuary. With the bellows regulation system still set at 3¼ inches, the windchest pressure became 3¼ inches.
During this time, the main HVAC blower was operating at 100% capacity (60 Hz) even though the blower system included a variable speed control. The following experiment was performed: the variable speed control was set to reduce the blower speed to 2/3 of full capacity (40 Hz), and the pressure differential between the sanctuary and the blower room was measured for both modes of operation—recycle with 15% air exchange and fresh air with 70% air exchange. The only change from the original HVAC settings is that the blower now operates at a lower speed. It was found that the pressure differential at 15% air exchange was 1⁄8 inch, and at 70% air exchange (recycle valve closed) was 1⁄16 inch. As expected, with the organ operating with the bellows regulating system set at 3¼ inches, the organ pressure was 33⁄8 inches at 15% air exchange (recycle mode) and 35⁄16 inches at 70% air exchange.
The bellows regulating system is now set at 31⁄16 inches, yielding an organ-to-sanctuary pressure of 3 or 31⁄16 inches in the two modes of operation—a difference of 1⁄16 inch, small enough that tuning is now not adversely affected. In addition, HVAC noise has been greatly reduced, and the air circulation in the sanctuary, while quite adequate, is less drafty for those sitting in the ends of pews near the walls, where the supply air vents are located.

Sanctuary acoustics
FPC Santa Fe underwent major renovation before Fisk Opus 133 was installed. This included considerable acoustic work in the sanctuary to prepare it for this fine instrument; much of the focus was on steps to increase the reverberation time. The chancel has diamond plaster side walls, which diverge slightly to help sound radiate into the sanctuary. The sanctuary has hardwood floors with minimal carpeting, hard plaster walls, and hardwood pews with reasonably reflective pew cushions. The ceiling was rebuilt with heavy plywood above latillas, and fine sand one foot deep was poured onto the plywood to help contain low frequencies from the organ. Although the reverberation time has not been measured, it is estimated to be about 1.5–2.2 seconds.
In addition to sound energy absorption each time a sound wave encounters a surface, sound energy can be lost through absorption in air. Absorption in air is a rather complex phenomenon involving molecular dynamics, and it varies with air density and relative humidity in a manner that is counterintuitive: thin, dry air attenuates sound more than thick, wet air. Furthermore, the attenuation varies with frequency. Table 1 provides values for attenuation at different frequencies for sea level and the Santa Fe altitude and for 10% and 50% relative humidity. Notice that absorption is greater at low humidity, high altitude, and higher frequency. At high altitude air is thinner and can hold less moisture; relative humidity of 12%–15% is not unusual on summer days in Santa Fe. To mitigate against the drying effects on organ components, a humidifying system is used to maintain relative humidity at around 40%; this also helps to reduce air absorption at higher frequencies.
In Table 1, the sound absorption is given in decibels per kilometer, which is just a little farther than sound travels during a reverberation time of 2.2 seconds. Figure 2 provides a plot of these attenuation data at sea level and in Santa Fe at 50% relative humidity.
Clearly, the attenuation is greater at high altitude and high frequency. However, to understand whether or not this will impact the sound of the organ in the sanctuary, the attenuation must be compared with reverberation decay, the decay in sound energy due to reflection off surfaces. This comparison showed that at 4 kHz, the air attenuation at sea level would be barely noticeable if at all, and would be completely negligible at lower frequencies. In Santa Fe a very astute listener might notice the lack of high frequency components after initial transients on a very dry day, but otherwise the sanctuary acoustics should be little affected by the high altitude.

Conclusion
The differences in organ acoustics and operation between sea level locations and Santa Fe are real and observable, but not severe. Judicious choices of windchest pressure for pre-voicing and voicing and better understanding of the HVAC system both have contributed to a very successful installation: Fisk Opus 133 is now performing regularly and brilliantly. It is hoped that these observations will serve others who choose to install a fine organ at similar altitudes.

 

Uwe Pape (edited by G. Nicholas Bullat)

Prof. Dr. Uwe Pape studied mathematics and physics in Göttingen. He was a professor of information systems at the Technical University of Berlin from 1971–2001, also serving as visiting professor at MIT in 1974 and 1984–85. His interest in organbuilding began in the 1950s, during his student days in Göttingen, when he encountered Paul Ott and his workshop. In 1959 he began an inventory of the organs of Braunschweig. In 1962 he established an organbuilding history publishing house. He is the author of many monographs in the field of north German organ construction. Since 1985 he has directed a research group for the documentation of organs and organ restoration projects. He is a consultant for institutions in Berlin, Bremen, Niedersachsen and Sachsen.

G. Nicholas Bullat, D.Mus.A., J.D., F.A.G.O., F.R.C.C.O., L.T.C.L, a former Dean of the Chicago AGO Chapter, served as chairman of the graduate studies division and organ and theory departments of the American Conservatory of Music, Chicago, and for many years was minister of music at First United Church of Oak Park, Illinois. After retiring from performing and teaching in the early 1990s, he practiced securities law at a large Chicago firm and was Vice President and Counsel at Harris Trust and Savings Bank, Chicago, until his retirement in mid-2005.

After more than 50 years of organ restoration activity in northern Germany, we have observed increasing demands for pre-restoration planning, process control, and submission of reports. Simultaneously, the scope of organ restoration expanded substantially, ranging today from the oldest existing instruments to electro-pneumatic organs of the 20th century. It is clearly not possible to create a uniform set of rules or principles for documenting this whole range: We may document an older instrument more carefully than newer ones; different information is desirable for different actions, etc.
The increased demands for proper documentation result not only from the technical advances of recent years, but also from the interests of the research and educational institutions and scientists involved in this topic. In the beginning, research projects were carried out by the institutions themselves,1 but today these services are also available from professional or commercial sources.2 The research and documentation capabilities of these institutions and similar organizations usually go far beyond those of organ builders, so that many organ builders now perceive these research projects as a meaningful addition to their own work and support these activities.
Many consultants are aware of these advances and interests, and have begun to expect that the organ builder carry out the needed research and provide the documentation. In practice, however, severe financial problems arise from the costs involved in carrying out this research with the required scholarly detail. Thus organ builders are encountering a new and significant (as well as expensive) requirement on the part of both congregations and experts as a result of this increased interest in documentation by the professional world. At the same time, many organ builders are also conscious of their obligation as restorers of historic instruments to meet at least some of these new requirements. The organ builder therefore must tread a via media between these new demands and reasonably pricing or financing the project—a true dilemma.

Development of restoration documentation in organ building

If we look at early restorations, we find that no actual reports were prepared until the 1940s, and find only relatively primitive attempts at documentation in correspondence and recordings in archives. If something was documented and, above all, photographed, it was usually the expert or consultant who did the work. Archives of organ builders may provide, from their project bids and invoices, some hints of the scope and nature of the work proposed and eventually carried out on a given instrument. If anything at all was documented, at least the specifications and perhaps rough drawings were preserved, but in general scalings and other significant details are not usually to be found. In many of these early projects we would be glad if we could find at least these data.
After World War II, some companies began maintaining written documentation, sometimes accompanied by a set of black-and-white photographs. Friedrich Jakob of the Theodor Kuhn organ company (Männedorf, Switzerland) writes that the AGSO (working group for the preservation of Swiss historic organs) was established in 1958.3 Subsequently, the first technical reports were developed in cooperation with Jakob; these ‘internal inventory reports’ were, however, substantially less detailed than the more developed restoration documents used today. The concepts compiled in these reports, which later provided the basic structure for full restoration documentation, were divided into the following sections:

A. Literature
B. Sources
C. Inscriptions
D. Inventory
1. Specification
2. Case including pipe order
3. Console including stop order
4. Wind chests, with slider and valve order
5. Key action
6. Stop action
7. Wind system
8. Pipe work, with scalings
E. Restoration suggestions

For the first time the relationships of façade, pipes, sliders and pallets were examined and recorded. This report format was expanded and refined in the following years. With two publications in 1965 and 1968,4 a level of standardization was reached, which at that time was judged by German specialists as exemplary and trailblazing. However, these were still not true and complete restoration reports, as they documented only an exact inventory of the instrument’s then-current state and provided only restoration suggestions.
In the 1970s, the expansion of this earlier form of report to real restoration reports that included detailed accounts of the work done, became standard in many large companies, as organ builders perceived and understood the need for comprehensive restoration information.5 In Germany, the Alfred Führer organ company of Wilhelmshaven6 was one of the first enterprises to provide more extensive reports, including:

1. History, with pertinent literature and sources
2. Case and façade pipes
3. Console
4. Wind chests
5. Key action
6. Stop action
7. Wind system
8. Pipe work, including scales
9. Temperament
10. Voicing7

German experts in church administration also developed large archives for organ documentation, of which the churches in Hannover and Magdeburg are well-known examples.8 It also became evident that extensive restoration reports, such as those provided particularly by the staff experts in museums of musical instruments, could be in the organ builders’ own best interests, by providing both a record of the work undertaken and a certain level of protection for the restorer against possible later challenges.
The main problem in this ‘museum approach’ was quickly identified, however: In general, a state or not-for-profit enterprise such as a museum doesn’t work under time pressure, and the costs of the documentation and scientific research are covered by an institutional budget. The situation in organ building is quite different: The costs of a report must be covered by the price of the restoration and, perhaps, by a special budget item or contribution of the congregation.
In some firms a combination of increased personal efforts and internal company restructuring made these more extensive reports feasible. Firms such as Theodor Kuhn (Männedorf), Johannes Klais (Bonn), Hermann Eule (Bautzen), and Alexander Schuke (Potsdam)9 set up their own restoration departments in which the chief restorer was also responsible for the full documentation of projects. A summary report on the entire restoration, supplemented by photographs and drawings, became standard.10 Newer organ companies have attached great importance to this documentation from their inception: Kristian Wegscheider (Dresden) is well known for his careful reports, which consist of a ‘condition report’ before the restoration as well as a later ‘restoration report’ on the work done; both are indispensable components of the process.11

Procedure and arrangement

Wolfgang Rehn (of Th. Kuhn AG) reports his personal ideas as a restorer and the requirements for documentation in a large restoration department.12 He developed a special model for documentation of restorations, in which he describes the report not only as an account of the work but also of the time and circumstances under which the work has been carried out. This report should take into consideration the requirements of the instrument’s period, e.g., the sense of musical style, the materials available, certain demands of consultants or architects, the importance of a light action, or the aesthetic sense and approach of the owner. If one can understand from the documents the conditions under and materials with which organ builders had to work at a certain time, one may better understand the work they actually were able to accomplish. In fact, this understanding may perhaps help to comprehend and preserve a certain building situation as the record of a great achievement of the time.
Documentation should also be seen as a ‘process report’. Typically we see only the finished picture, not how it came to be, whereas we want to comprehend more thoroughly the work itself and the various influences on it. Until a few years ago a project was usually documented and presented only in summary fashion, perhaps even somewhat favorably colored or highlighted. No one would mention errors, misjudgments, and false estimates. Many matters and decisions later criticized or even condemned may be much better understood if we knew why or how they were done or reached. We may even discover a level of respect for what may be an inadequate execution when working conditions are better known. For these reasons we should try to find a way to utilize the technical achievements of our times, thus responding to modern demands while at the same time holding the expenditure of time (and money) to reasonable orders of magnitude.
The Kuhn company sought to merge the documentation process as far as possible with the regular work routine, seeing it to a certain extent as a by-product of its work planning. The adjustment of the documentation process to the work schedule also led to another and more objective overall report. As opposed to earlier methods, this new kind of documentation became a collection of data subsets encompassing the entire restoration period.

The Kuhn model

From the beginning of the 1990s the Kuhn company ceased preparing final restoration reports, instead arranging the production plan and the information data simultaneously as total project documentation. In order to obtain a consistent overview, this sequentially written report always has a similar arrangement of the individual parts. Thus if one looks for statements about, e.g., wind chests, one can easily find the inquiry results, recommendations, resolutions, and all related remarks in a certain place in the contents of each report. Each report part is regularly provided with an appendix of photographs. The arrangement used by Kuhn is as follows and may be taken as a model for documentation reports in general:

A. Initial situation
1. Basis
2. Problem
3. Historical outline
4. Specification (existing)
B. Report
1. General condition
2. Pipe work
3. Key action
4. Stop action
5. Wind chests
6. Console
7. Wind system
8. Case and framework
C. List of requirements

Sections A1 and A2 describe the initial state of the instrument and terms of reference. Sections A3 and A4 discuss the historical development of the instrument and list the specification(s) with all major changes. It is in general an excerpt of documents from church archives and may be supplemented by facsimiles of bids, contracts, and/or certificates.13
Each part of section B consists of four elements.

1. Project bid
The first part of the restoration report begins with the project bid, because the investigation report for the bid is the first part of the overall report. Unfortunately it is not possible to include the competing project bids of the other firms here also, even though this would result in a more complete picture for later readers.

2. Disassembly Report
The second part of the restoration report, the disassembly report, is definitely the most complex and most important part of the total documentation. The following approach to inventory and description of pipes serves as an example of the importance of this documentation:
All pipes are noted in the account sheets prepared for the corresponding organ with measurable and computable values—scalings of circumferences, lengths of bodies and feet, widths of toe-holes, mouth widths, cut-ups and number of nicks. If pipes are of different design, these are described exactly and illustrated by photographs. The analysis of alloys may be provided by companies for material testing.14 Very important is the investigation of inscriptions [any markings on the pipes, e.g., pitch indications, maker’s marks, etc., known as Signaturen]. These are copied by hand and transferred to special documentation sheets with information describing their placement on each pipe. A specific or unusual Signatur characteristic may also be photographed in all octaves. (See illustrations.)
Of course this investigation and recording of information must have reasonable limits. While it is clear that there are still more possibilities concerning pipe documentation, it is important not to strive for accuracies that are beyond reasonable measurement. We apply the principle: better no data than incomprehensible or incorrect data. Rehn gives several examples such as wall thickness of small pipes and pipes with coned-in feet. How many measurements are reasonable? Another example is the measurement of the windway and the languid bevel. Here one could demand a multiplicity of values at each languid. Further examples are also the depth and placement of nicks, or which file profile has been used in the nicking process. These characteristics are much more relevant to a pipe’s sound than the second decimal place of a scale’s diameter. Another example may be the analysis of the partials produced by each pipe of an organ. Thus the actual tonal condition can be exactly documented. But what is the use of a documentation of the sound of dirty pipe work? We would have to measure the sound characteristics again after cleaning. And we have to do this yet again after the restoration in order to document the result and any changes. Does this make sense? If we recognize that the third partial tone is weaker than it was in the second measurement, what do we do then?
Demands and expenditure can become limitless in light of the possible scientific measurements. The costs of the documentation of the pipe work alone in a large organ can thus easily reach five- to six-digit Euro or dollar amounts. Therefore, in practice we must limit ourselves to the values specified above. These permit us to make an exact copy if necessary. From these data later substantial changes, e.g., changes of cut-ups and toe-hole openings, are readily understandable.

3. Project Elaboration
In this section of the report the results of the investigation process are converted into a work program and its documentation. Continuing the example of the pipe work, we can see how the documentation at the same time becomes a tool in the workshop: Decisions concerning allocation of and actual work on the pipes follow the description of the registers from the investigation in accordance with their manufacturing method and Signaturen. Along with this process a classification table may be provided to ensure an overview during work on the project while also allowing a later comprehensive representation of the project.
This example shows how the documentation becomes to a certain extent a by-product of the work. The other parts of the organ are documented in the same way during the restoration process. Apart from these remarks all minutes of meetings and the resolutions of issues raised are also attached in this section of the report.

4. Implementation
The last part of the restoration report summarizes briefly which portions of the plan were definitely implemented. This part is deliberately brief because more detailed reporting would result in additional expenditure that has no real relation to the craftsmanship. It consists mainly of references to necessary parts of sections 2 and 3, and, if necessary, supplements any deviations from plan.

Summary

Restoration reports should compile and obtain as much meaningful information as possible. Rehn emphasizes that details should be written to explain that “We implemented the following—and these are our reasons.” Although including such details may be viewed as ‘make-work’ in connection with organ restorations, one must admit that there may be a real need for such remarks in individual cases, and that how and why actions were undertaken should be made clear in a report. Glossing over facts, rationales, and ideologies should not be allowed.
As the financial support available for the documentation of a restoration is usually very limited, the organ builder must work as efficiently as possible. The approach described above provides a useful method and reasonable result.

*This article was edited by Dr. G. Nicholas Bullat.

Abstract 

Whether mechanical organ actions allow organists to control the way in which they move the key and thus influence the transients has been discussed for many decades, and this is often given as their main advantage. However, some physical characteristics of mechanical actions, notably pluck, make it difficult for the player to control the key movement and thus vary the transient. This project looks primarily at how organists use rhythm and timing to play expressively, but also provides some evidence about whether transient variation is significant. Rhythmic variation can be through the use of deliberate “figures”, or the player may be unaware that they are making such variations. These variations in style lead to clear groupings of the pressure rise profile under the pipe and thus limit the amount of transient control possible. This is supported by informal listening tests. It also considers other factors that might lead to transient variation that are outside the player’s direct control.

Introduction 

This paper presents results from a project funded by the UK Arts and Humanities Research Council at the University of Edinburgh and is based on papers presented at ISMA 2010 (International Symposium on Musical Acoustics) in Australia¹ and Acoustics 2012 in Nantes.²  The organ has been described as a “dangerously inexpressive” musical instrument.³ The project set out to investigate the extent to which organists use rhythm and timing to achieve expression on mechanical action pipe organs rather than varying the transient by the way in which they move the key, although it inevitably also considered the latter. Transient control is widely considered a basic factor of organ playing but this is not universal, and a number of prominent organists and builders, such as Robert Noehren,⁴ disagree. However, there is little published research about this or whether other mechanisms may be important for expressive organ playing. 

This project originally started because  of the construction of a number of large organs in the UK that have dual mechanical and electric actions. The curators of these organs reported that the mechanical consoles were hardly ever used, suggesting that any advantage was not overwhelming. It also implied that there may be significant unnecessary expenditure and also the possibility that either or both of the actions were compromised. 

The PhD work that preceded this project concluded that players did not vary the way in which they moved the key to the extent that they thought they did.⁵

Background 

The bar (groove) and slider windchest has existed more or less unchanged for some 600 years even down to the materials generally used. 

The one characteristic that defines the nature of the touch of a mechanical pipe organ action is pluck (being analogous with the feel of the plectrum plucking the string of a harpsichord. It is also called “top resistance”). Pluck is caused by the pressure difference across the closed pallet (H) in Figure 1, which is a modification of an illustration by Audsley of a cross section of a bar and slider windchest.⁶ The bar is the channel on which all the pipes for one note are planted. The sliders (S) are movable strips, traditionally of wood, that determine which ranks of pipes receive air from the groove, by lining up holes in the slider with corresponding holes on the top of the groove. They move perpendicularly to the plane of the diagram. With the pallet closed, the pallet box (ABDH) contains pressurized air whereas the groove contains air at atmospheric pressure. The net force of the pressurized air on the bottom of the pallet has to be overcome in order for the pallet to start opening. As soon as the pallet starts opening as the tracker (attached to N) moves downwards, the pressures on either side of the pallet start to equalize and the additional force reduces very quickly (Figure 3). The feeling has been likened to pushing a finger through a thin layer of ice. 

When a note is not sounding, the pallet is kept closed by the force exerted by the pallet spring (G) and the air pressure  against its lower surface. As a force is applied to the key, the various action components bend (key levers, backfalls), twist (rollers), stretch (trackers) and compress (cloth bushes), etc., until sufficient energy is stored to overcome the force keeping the pallet shut. Figure 2 shows a 200g key weight on a key of the model organ in Edinburgh just before the pluck point, with the pallet still closed. The key is depressed by about 40% of its total travel. Any further movement will result in the pallet immediately opening by a similar amount before the key has moved significantly further—the pallet “catches up” with the rest of the action. 

The need to keep the playing force and repetition rate within acceptable limits means that the action can never be made completely rigid, and it will always act like a spring to some extent. The basic characteristics of the movement of a key through to the sounding of the pipe are illustrated graphically in Figure 3. 

The low frequency variation in the pressure at the beginning of the note is due to the delay of the pressure regulator, described more fully later, and the high-frequency component throughout is due to the pipe feeding back into the groove. The most important features of Figure 3 are: 

• The key moves a significant distance before the pallet starts to open and catches up with the rest of the action ~ 40% 

• The key slows down due to the increasing resistance as the action flexes (rollers twisting, washers compressing, levers bending, etc.) 

• As the resistance due to pluck is overcome, the key increases in speed of movement, as it is not possible to reduce the force being applied by the finger in the time available 

• The air pressure in the groove starts to rise at the same time as the pallet starts to open 

• The force applied to the key increases until just after the pluck point, when it reduces, although not suddenly. This is probably due to the airflow through the pallet opening applying a closing force to the pallet 

• The force increases suddenly as the key hits the key bed 

• The air pressure reaches a peak early  in the pallet movement (after about 45% pallet travel) 

• The pallet starts to open at about 40% of key travel and the pressure in the groove reaches a maximum at about 57% key travel. This is the only part of the key movement that could affect the transient, but during this movement the  pallet is out of control of the key because  it is still catching up with it 

• There is a delay before the pipe starts to speak 

• The key is on the key bed and the pallet is fully open before the pipe has reached stable speech 

• There is a delay before the pallet starts to close when the key is released (probably due to friction) 

• Later in the release movement the pallet starts to close in advance of the key movement (due to air pressure) 

• The pallet is firmly seated before the key has returned to its rest position (in this case the key has 23% travel to go) 

• The sound envelope does not start to diminish until the point at which the pallet closes 

• During the key release, the force is gradually reduced but the key does not start returning until the force due to the  pallet spring is greater than the force applied by the finger 

• There is slight increase in force as the pallet “snaps” shut due to the flow of air through the opening. This helps to reduce leaks around the closed pallet, but would also make it very difficult to control the pallet in the final stage
of travel. 

The time of travel of the pallet from starting to open to fully open is typically  around 30ms (0.03 seconds). Reaction times in sporting events are generally around a best of 100ms.⁷ This implies that the player is unlikely to be able to respond to pluck and reduce the force being applied by the finger. 

These effects were noted in every organ measured, to a greater or lesser extent, depending on the size and rigidity of the action and the magnitude of pluck, and even on a light, suspended action the effect is significant. 

Initial work

Some tests were carried out with the University of Edinburgh organist, Dr. John Kitchen, playing the 1978 Ahrend organ in the Reid Concert Hall. This has a very “light” suspended action (50g key force, 50g pluck, Hauptwerk, middle C Principal). In the first exercise he played an improvised theme and was then asked to repeat it, varying nothing but the speed of key movement. The measurements of the key movements are shown in Figure 4, in which the curves are superimposed on the main part of the key movement rather than the pluck point.⁸ Kitchen felt that he had moved the key “five times faster” the second time (black curve) and changed nothing else. In fact, the time from the key starting to move to hitting the key bed in the fast note was about half the length of the slow note, with all of the difference at the beginning. Figure 4 does not show that the overall tempo was also faster with the fast key movement, but it can clearly be seen that the fast attack has resulted in a significantly shorter note. Even on this relatively rigid action, the effect of pluck is apparent at the beginning of the key movement at about 0.8mm key travel. 

In the next exercise Kitchen tried to accent a note by “hitting it harder.” Figure 5 shows that again with the non-accented movement the effect of the flexibility of the action is apparent, but the majority of the movement is very similar in both cases. 

In the two previous examples, the main part of the key movement has been superimposed. Since the relative timing of the pluck point varies, a further test was designed to indicate the point at which the player perceived the note to start. He was asked to play in the two manners from Figure 4 one octave apart simultaneously. Figure 6 shows the two notes to the same time reference and indicates that the player perceived the start of the note to be the point at which the key started to move. This introduces a timing difference between the two notes of approximately 30ms as the pipes will not start to speak until after the pluck point at a displacement of approximately 10% of travel. The “slow” note will sound after the “fast” note and is also slightly longer by about 10ms. The differences between the shapes of the beginnings of the key movements are discussed later. It is interesting that the notes do not end simultaneously. 

A further exercise was carried out at the Canongate Kirk in Edinburgh (Frobenius 1998, IIP20). A simple visual examination (confirmed by informal listening tests) shows that distinctly different key movements are not reflected in the sound profiles. Figure 7 represents a “fast” attack and Figure 8 represents a “slow” attack as perceived by the player. As observed throughout, the “slow” attack also resulted in a longer note. 

Rhetorical figures 

A frequent comment by organists was that even if it were possible to vary the way that they moved the key at the start of a piece of music, it was not possible to maintain these variations throughout a piece. Dr. Joel Speerstra is studying rhetorical figures at the University of Göteborg, based on his research into clavichord technique. These are physical gestures that can be maintained throughout a performance and are based on rhetorical figures in German baroque music described by Dietrich Bartel.⁹ 

Examples of Speerstra’s figures are listed below with his descriptions,¹⁰ along with graphs of some of these showing the key movements, pallet movements, pressure rise in the groove, and sound recordings. The measurements taken showed that phrasings closely followed the descriptions given, and some examples are shown below. 

Transitus (Figure 9) 

“You are standing a certain amount of the weight of your arm on a stiffened finger with a relaxed elbow, and moving from the first finger to the second without completely engaging the muscles of your arm that would lift it off the keyboard. This technique makes it easy to control heavy actions, and you would expect this kind of paired fingering to have fast attacks for both notes and a longer first and third note a shorter second and fourth note and, hopefully, as slow a release as possible after the second and fourth note.” 

The releases of the second and fourth notes are not significantly different from the others. 

Suspiratio (Figure 10) 

“It is a figure that starts with a rest followed by three notes, so the first note is now an upbeat, and I would expect that there is a faster release after the first note, and the second and third would form a pair much like the first and second in the transitus example.” 

Portato (Figure 11) 

“Portato [uses] separated notes but with slower attacks and releases.” 

To these can be added more familiar styles such as legato and staccato, although these may benefit from being more clearly defined. Whenever players were asked to play fast attacks, they also played shorter notes. 

Measurements were made of Speerstra playing in these styles on the North German organ in the Örgryte Church in Göteborg (built in the style of Arp Schnitger by the Göteborg Organ Art Centre [GOArt] as a research instrument). The key movement (middle C, D, E, F), pallet movement (C, D) and pressure in the groove of middle C (measured by removing the Principal 8′ pipe) were measured, as well as sound recordings being made. All magnitudes are to an arbitrary scale. 

Figure 12 shows all of the key movements and pressure profiles for the rhetorical figures described above. Despite the low number of data points, it can be seen that there are two groups of key movements and two very close groups of pressure rise profiles. The graph has been produced to show the two groups superimposed within the group but separated between the groups. If the player perceives the note starting at the point at which the key starts moving, there will also be time differences between the start of the notes as in Figure 6 above. There is an initial pressure drop in the “faster” group. Full listening tests have not been carried out, but initial tests across a wide range of musical levels did not indicate consistent differences in flue pipe transient between styles, although highly trained ears will detect subtle changes that others may not be able to. Reed pipes were not included in this study, although clear control of the final transient of some of the solo reeds was apparent when played in isolation. 

This organ is unbushed and there is a considerable range of noise response from the action—from almost silent to distinctly audible in the church, depending on the performer’s technique. This noise can mask the attack transient of the pipe, particularly close to the console. This issue was also encountered later in Rochester, and Speerstra considers that playing in a way that causes excessive noise is both undesirable and avoidable. John Kitchen also stated that he played in a style that minimizes the action noise on the Ahrend organ in Edinburgh. This avoidance of excessive action noise may limit variations in key and thus pallet movements. Excessive noise on key release may also mask the release transient. 

An example from each group is shown in the following graphs. Figure 13 illustrates an example from Group 1 and shows a relatively gradual start of the key movement, the first in the sequence. The accent is on the second note of the sequence.

Figure 14 shows a comparable note from Group 2. The key initially accelerates quickly and shows a distinctly different form of movement from Figure 13. The accent is on this note. 

The initial movement of the key is fundamentally different, and tests on the model at Edinburgh indicate that in the case of the portato playing style, the finger was in contact with the key at the start of the movement, whereas in the transitus example, the finger started its movement from above the key and thus was moving with significant speed when it contacted the key, causing a much greater acceleration of the key. 

Measurements were also made on the copy of the Casparini organ of 1776 from Vilnius, Lithuania, built by GOArt in Christ Church, Rochester, New York, for the Eastman School of Music (ESM). A number of doctoral organ students played in styles of their choice that they considered resulted in variations of expression, including different transients. They used their own descriptions of these styles; some of these were long and descriptive and cannot be incorporated onto the graphs. The pressure was measured directly under the pipe foot using a device made by the ESM organ technician Rob Kerner, and is not directly comparable with the previous example. The groupings of pressure rise profile have again been superimposed to highlight the similarities, and the time scale does not represent a constant start point of the note. All recordings are of the same theme used in the previous exercise.

Figure 15 shows the measurements from the first student, CP. There appear to be three distinct groups. The initial gradient of the first group shows some variation, but again, initial listening tests did not consistently identify differences even between the two extremes. The other two groups are more closely matched. It is not clear why there is a pressure reversal in group 2. Note again the initial pressure drop in group 3 and the extreme pressure variation. It is not yet clear what differentiates group 3 from the others. There were significant variations in the overall tempo, length of individual notes, relative lengths of adjacent notes, and overlap of notes.

The student’s description of each of the styles is shown in the following tables:

Table 1. Descriptions of playing styles in Group One, Figure 15. Student CP

259	Classical Mendelssohn
260	Romantic pp
262	Romantic pp
265	Baroque, two beats per measure
269	Bach 1st inversion suspiratio
270	Legato

Table 2. Descriptions of playing styles in Group Two, Figure 15. Student CP

256	One accent per measure
257	One accent per measure
258	Classical Mendelssohn
267	Baroque, one beat per measure
268	Baroque, two beats per measure
271	Harmonized

Table 3. Descriptions of playing styles in Group Three, Figure 15. Student CP

263	Virtuosic light ff
264	Virtuosic light ff

Two styles, 265 and 268—Baroque two beats per measure, and 258 and 259—Classical Mendelssohn, fall into both groups one and two, implying a fundamental difference between the two finger movements.

The key movements of the two extreme styles, Romantic pp and Virtuosic light ff, are shown on page 26. Figure 16 shows Romantic pp (262).

Figure 17 shows “Virtuosic Light ff” (263) to the same scale. It is unnecessary to state that the overall tempo is different.

Figure 18 shows the measurements of the first note in each sequence from student LG. Here there are two groups for the Principal 8′ alone, corresponding with groups one and two of CP’s playing. The measurements from the plenum are not readily distinguishable from the Principal alone. 

The descriptions of the styles are:

Table 4. Descriptions of playing styles in Group One, Figure 18. Student LG

274	Normal
277	Weight on 2nd
278	Weight on 2nd
283	Plenum equal accents
284	Plenum accent on 1st of pair
285	Plenum accent on 1st of pair
286	As 285 but faster tempo

Three of these are played on the plenum and not a single stop as with the others.

Table 5. Descriptions of playing styles in Group Two, Figure 18. Student LG

273	Normal
275	Paired notes with more weight on 1st
276	As 275
280	Weight on 2nd, 3rd and 4th finger
281	As 280
287	Fast, stronger on 1st

All of the pallet movements are shown in Figure 19. There is little difference in the initial movement, even though there were much wider variations in the key movements (Figures 20–22). There is very little difference in the key releases, but with two exceptions. In the case of examples 277 and 278, “Weight on 2nd” (marked with X on graph 17), there was a distinct elongation of the pre-pluck part of the key movement and the key, and thus the pallet did not reach full travel. As the pallet stopped at exactly the same point in each case (the key stopped at very slightly different points), it seems probable that there was high friction at this point. The attacks of these two key movements produced a shallower gradient at the start of the pressure rise, although informal listening tests did not indicate that this variation was sufficient to produce an audible difference with the single stop used in this test. The key and pallet movements for one of these are shown in Figure 20. The two “Normal” playings are split between the two groups, which again suggests a very distinct difference between them.

The curves are in sequence of time of closing and are from left to right, using the numbers in Tables 4 and 5, 278, 277, 287, 280, 274, 273, 286, 276, 281, 284, 285, 283. The consistency in speed of closure is worthy of note. The two curves at P are for the plenum and not a single pipe. It is possible that two non-accented notes marked with X would have closed similarly to the others had the pallet not stopped part way. There is a wide variation in the length of the notes and the overlap with following notes.

Two of the plenum notes in Figure 19 are marked with P at the point at which they cross. One of them shows a slower release of the pallet, whereas the other is similar to the rest of the movements. The key and pallet movements of the slower release are shown in Figure 21. This clearly shows that the pallet shuts before the key is fully released as shown in Figure 3. The key movement slows down when the pallet is no longer being pulled shut by the airflow round it.

Figure 22 is an example of a typical key and pallet movement, no. 275 “Paired notes with more weight on 1st.” Note that in all of Figures 20–22 the pallet does not start closing until after the key has started moving, indicating a degree of friction in the action.

Comparing Figure 20 with Figure 22, the weak note in Figure 20 has resulted in an extended pre-pluck movement of the key compared with the strong note in Figure 22. This is not reflected in the pallet movements to the same extent and, as discussed above, may result in timing differences in the sounding of the pipe if the player perceives the note as starting when the key starts to move.

All of the six student subjects demonstrated significant groupings of pressure along the lines of the examples shown above.

Key release 

Throughout this project, players have stated that even if there may be reasons why the attack may be difficult to control, it is possible to control the release accurately. There seems little evidence that this is actually the case.

While it is possible to control the initial movement of the key during the release stage because there are no similar effects to pluck, this does not necessarily allow for control of the ending transient. In the same way that the pressure in the pipe foot reaches its peak very early in the pallet opening it starts to reduce very late in the pallet closure. The corollary of pluck is felt as the airflow around the nearly closed pallet starts to “suck” it shut. Due to the flexibility in the action, the pallet closes before the key has returned to its rest position. Also, because the key force reduces due to this effect it is very difficult for the player to control the last part of the key release.

Some key releases were recorded at Göteborg. A fast release is shown in Figure 23 and a slow release in Figure 24. The blue line is the key movement and the pink line the sound recording.

By editing the steady part of the slow movement out to make the notes the same length just leaving the transients, informal listening teats confirmed that there is no difference in the sound of the transients. The difference between the notes is that the slow release results in a longer note.

Pressure changes in the wind system

In most organs the pressure regulator is remote from the windchest. Any variation in the air supply, such as when a note is sounded, will not be immediately compensated for. There will therefore be an overall pressure reduction when a note is started and a pressure increase when it is released. This was investigated by Arvidsson and Bergsten at GOArt in 2009.¹¹ This has been extended at Edinburgh to consider how these pressure waves in the wind system might affect pipe speech. Figure 25 shows a single note being played, and it can clearly be seen that the pressure in the pallet box reduces as the pallet opens, oscillates for a few cycles, and then steadies. This is reflected in the pressure measured under the pipe foot and also in the sound envelope of the pipe speech. When the pallet closes there is a corresponding increase in pressure. The variations shown here are around 35% of the steady pressure. These measurements were made on the model organ in Edinburgh and, while the effect will occur in any organ, the magnitude of these effects may be greater than normally encountered. A schwimmer system will reduce these effects.

Figure 26 shows the effect of playing a note before the note being measured. The pipe of the first note, E, was removed so that its sound did not interfere with that of the pipe being investigated. It can be seen that the effect of the release of the first note and of the attack of the second, F, have resulted in an even greater variation in the pressure throughout the wind system, and this is reflected in the outline of the sound recording. Listening tests have not been carried out, but this may lead to an audible difference in the transient of the second pipe.

Many notes being played together will produce large and random pressure variations in the wind system. These effects are also apparent with electric actions.¹²

It should also be noted that since pluck is directly related to the pressure in the pallet box, it will vary in proportion to it. It is thus possible that a momentary change in the magnitude of pluck could influence the time at which a key is depressed—especially if the player is already applying some force to the key.

Length of transient

In Figures 27 and 28, played on the ca. 1770 Italian organ in the Museum of Art, Rochester, New York, the pipe is slow to speak and starts at the octave and then breaks back to the fundamental. 

If a short note is played, as when the player is asked to make a “fast” attack, most of the pipe speech will be at the octave and that is what the listener perceives as the pitch of the note.  If a longer note is played, most of the pipe speech will be at the fundamental, and that is what the listener will hear. If the player is expecting a variation in transient, he may associate the different perceived sounds with what he believes are different key movements. In Figure 27, there is also evidence of initial mechanical noise. Note again that the nature of the attack has been reflected in the length of the note.

Conclusion

There is clear evidence that rhythm and timing are critical aspects of organ playing. In some cases they are the result of deliberate and systematic efforts by the player, as in the use of rhetorical figures, and in others the players may be unaware that they are making variations. Analysis of the various performances of the same sequence of notes showed wide variations in overall tempo, relative lengths of notes, and degree of overlap of notes, all of which will affect how it sounds to the listener. These and some other effects like variations of pressure in the wind system are independent of the type of action.

There is some evidence that transient control is difficult to achieve by the inherent design of the mechanical bar and slider windchest. Variations in key and thus, to some extent, pallet movement cause the pressure rise in the pipe foot to fall into distinct groups, the reason for which is still under investigation but would appear to be due to whether the finger starts in contact with the key or is already moving from above the key when it starts the note. Whether these differences result in audible changes is not clear and is likely to vary from organ to organ, and it is necessary to carry out properly controlled listening tests. Action noise may be a factor in informal listening tests. The player cannot react to pluck and any variations in key movement are predetermined.

Many of the characteristics of the bar and slider windchest work against transient control and this may have been one of its advantages—the aiding of clean consistent attacks due to the rapid opening of the pallet when pluck is overcome, but there is clear empirical evidence that players like mechanical actions. The immediate reason for this may be that it provides good tactile feedback. The organist can apply a certain force to the key in the certain knowledge that the note will not sound, but the force reduces to a comfortable level when the key has been depressed. It may also help reduce the risk of accidentally sounding a note if an adjacent key is brushed. 

It is unlikely that the original builders of the first windchests applied theoretical fluid dynamics to the design, and other reasons for its endurance may include:

• Ease of construction

• Reliability

• Ease of repair

• Snap closing of the pallet to give a good seal.

Every organ is different and this project has been limited by the instruments available. While this work may suggest that direct transient control is difficult, this may not be the case on instruments with different characteristics. There are, however, other mechanisms in play that may explain different perceptions of the sound.

This project is continuing and, with the cooperation of our colleagues around the world, it is expected that a clearer understanding of these important issues will emerge. 

Acknowledgements

My thanks to the Arts and Humanities Research Council, Professor Murray Campbell and Dr. John Kitchen at Edinburgh, the staff and students of GOArt and the Eastman School of Music, Joel Speerstra for his very helpful review of this article, Dr. Judit Angster and Professor Andras Miklos, Laurence Libin, John Bailey of Bishop and Sons in Ipswich, David Wylde of Henry Willis and Sons in Liverpool, and many others.

Notes

1. Alan Woolley, Mechanical Pipe Organ Actions and why Expression is Achieved with Rhythmic Variation Rather than Transient Control (Proceedings of ISMA, Sydney and Katoomba, 2010), paper number 2.

2. Alan Woolley, How Mechanical Pipe Organ Actions Work Against Transient Control (Proceedings of Acoustics 2012, SFA, Nantes, 2012), paper number 410, pp. 1969–1974.

3. Stephen Bicknell, “Raising the Tone,” Choir and Organ (March/April 1997), pp. 14–15.

4. Robert Noehren, An Organist’s Reader (Michigan: Harmonie Park Press, 1999), p. 161.

5. Alan Woolley, The Physical Characteristics of Mechanical Pipe Organ Actions and how they Affect Musical Performance (PhD Thesis, University of Edinburgh 2006).

6. George Ashdown Audsley, The Art of Organ Building (Mineola: Dover, 1965 republication of 1905 edition, Dodd, Mead & Co.), p. 215.

7. International Amateur Athletic Association, Rulebook, Chapter 5, Rule 161.2.

8. Alan Woolley, “Can the Organist Control Pallet Movement in a Mechanical Action?” (Journal of American Organbuilding, December 2006), pp. 4–8. 

9. Dietrich Bartel, Musica Poetica: Musical-Rhetorical Figures In German Baroque Music (University of Nebraska Press, 1997), pp. 57–89.

10. Discussion with author.

11. Mats Arvidsson and Carl Johan Bergsten, Wind system measurements in the Craighead Saunders organ (GOArt 2009), unpublished.

12. Alan Woolley, Transient variation in mechanical and electric action pipe organs (Proceedings of Meetings on Acoustics, Acoustical Society of America, Montreal June 2013, Volume 19), Paper no 4aMU3.