Organ Acoustics at High Altitudes

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.

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 Bishop is executive director of the Organ Clearing House.

Wind
I’m a nut for a good wind. We live by the ocean, and I never tire of the feeling of the wind coming off the water bringing fresh air and all the good tidal smells into the house. I love to open the sliding doors that face the water and a door at the other end of the house to create a wind tunnel. (It’s not always popular with other family members.)
Years ago I was active in a small inland sailing club on the shore of a lake in the center of a suburban town. The lake was less than two miles north-to-south, and less than one mile east-to-west, so you couldn’t go for very long without coming about (turning to take the wind on the other side of the boat).
Since ours was a single-class racing club, the size of the lake didn’t matter. Depending on the speed and direction of the wind, the race committee set a course using inflatable markers (yellow tetrahedrons) with anchors. The classic Olympic sailing course uses three marks labeled A, B, and C set in an equilateral triangle. A is directly upwind from the starting line, C is directly downwind, and B is to the left, so boats go clockwise around the upwind mark. The basic course is A-B-C-Finish, but you can add an extra lap or two, and we often modified it to read A-B-C-A-C-Finish. These patterns would expose all the sailors to all points of sail as they went around the course.
One drizzly afternoon I headed the race committee. The wind was northerly, so I set the upwind mark close to the northern shore. A few minutes after the start, I noticed that the entire fleet was heading in the wrong direction. These were pretty good sailors, and it would be unusual for the whole group to get the course wrong. They were following what looked like a yellow tetrahedron that was a little east of upwind—a fellow in a yellow slicker and a yellow kayak who was heading away from the mark! I flew the recall-signal flag and started the race again, but not until we had all had a good laugh.

Know your wind
To sail a small boat is to be intimate with the wind. You have telltale streamers on the sails so you can tell exactly where the “lift” is and you watch the surface of the water for the ruffles that indicate the presence of wind. When there’s an updraft on the shore, air rushes in off the water to fill the void—so hawks, ospreys, and eagles soaring can tell you something about the wind on the water. In fact, this is the cause of a “sea breeze.” When the sun heats up the land in the afternoon, air rises off the land and the cool air rushes in off the water to take its place. Where we live, you can have a quiet picnic in the boat around twelve-thirty and put your things away in time for the sea breeze to come in around two in the afternoon.
If you sail often in the same place, you get used to how the wind comes around a certain point, swirls in a cove, or rushes directly from the sea toward the land depending on the time of day. There was an old salt at that inland club who had figured out how to predict the local wind by observing which direction airplanes were traveling to and from Boston’s Logan Airport twenty miles away. During a race you’d notice him heading off alone to some corner of the lake only to pick up the strongest wind of the afternoon and shoot across to a mark ahead of the rest of the fleet. I never did figure out how that worked, but he sure won a lot of races.

§

The steadiness, reliability, and predictability of wind is a huge part of playing and building pipe organs. We compare “wobbly” with “rock-steady” wind, debating their relative musical merits. One camp hates it when the organ’s wind wiggles at all (ironically, those are often the same people who love lots of tremolos!), the other claims that if the wind is free to move a little with the flow of the music, there’s an extra dimension of life. I think both sides are right. I love good organs with either basic wind characteristic, but because they are so different it seems awkward to try to make real comparisons. The instrument with gentle wind that makes the music of Sweelinck sing does not do well with the air-burning symphonies of Vierne or Widor.
As a student at Oberlin in the 1970s, I spent a lot of time with the marvelous three-manual Flentrop organ in the school’s Warner Concert Hall. The organ was brand new at the time (dedicated on St. Cecelia’s Day of my freshman year) and is still an excellent study of all the characteristics that defined the Classic Revival of organbuilding. It has a large and complete Rückpositiv division (Rugwerk in Dutch) and a classic-style case with towers. There are independent sixteen-foot principals on manual and pedal, and the whole thing was originally winded from a single wedge-shaped bellows behind the organ. End a piece with a large registration and make the mistake of releasing the pedal note first, and the wind slaps you in the back, giving a great hiccup to the grand conclusion.
As students, we worked hard to learn to control the organ’s wind, marking in our scores those treacherous spots where the wind would try to derail you. There were no hawks there to warn about the updrafts. A little attention to the lift of your fingers or a gentle approach to the pedal keys would make all the difference, and I remember well and am often reminded that such a sensitive wind system can be very rewarding musically.

Totally turbulent
It’s interesting to note that while the older European-style organs are more likely to have unstable wind supplies, organs like that were originally hand-pumped and had more natural wind that anything we are used to today. The greatest single source of turbulence in pipe organ wind is the electric blower. Because the wind is hurried on its way by a circular fan, the air is necessarily spinning when it leaves the blower. If the organbuilder fails to pay attention to this, the organ’s sound may be altered by little tornados blowing into the feet of the pipes.
I learned this lesson for keeps while renovating a twelve-stop tracker organ in rural Maine ten years ago. Before I first saw the organ, the organist said that the sound of the Great was fuzzy and strange, but the Swell was fine. Sure enough, she was exactly right, and I was surprised by the stark contrast between the two keyboards. Every pipe of the Great wobbled like the call of a wild turkey.
This was the ubiquitous nineteenth-century American organ, with an attached keydesk and a large double-rise parallel reservoir taking up the entire floor plan. There were wedge-shaped feeder bellows under the main body of the reservoir and a well at each end to provide space for the attachment of the square wooden wind trunks. In the 1920s an electric blower was installed in the basement some thirty feet below the organ, and a metal windline was built to bring the air to the organ through a crude hole cut in the walnut case (Oof!). The easiest place to cut into the organ’s wind system was the outside face of the Great windtrunk—piece of cake. But the effect was that the Great was winded directly from the violently turbulent blower output, while the wind had to pass through the calming reservoir before it found its way to the Swell. Every wiggle and burble of the wind could be heard in the sound of the pipes. Relocating that blower windline sure made a difference to the sound.
That lesson was enhanced as I restored a wonderful organ by E. & G. G. Hook in Lexington, Massachusetts. Part of that project was to restore the feeder bellows and hand-pumping mechanism so the instrument could be blown by hand or by an electric blower. Of course, it’s seldom pumped by hand, but there is an easily discernible difference in the sound of the organ when you do.
The introduction of electric blowers to pipe organs must have been a great thrill for the organists of the day. Marcel Dupré wrote in his memoir about the installation of the first electric blower for the Cavaillé-Coll organ at St. Sulpice in Paris, where Charles-Marie Widor was organist between 1870 and 1933. I have no idea just when the first blower was installed, but it was certainly during Widor’s tenure, and it must have been a great liberation. I suppose that for the first forty years of his tenure, Widor had to arrange for pumpers. That organ has a hundred stops (real stops!), and pumping it through one of Widor’s great organ symphonies must have consumed the calories of dozens of buttery croissants.
Since electric blowers became part of the trade, organbuilders have worked hard to learn how to create stable air supplies. A static reservoir in a remote blower room is the first defense against turbulence. We sometimes attach a baffle-box to the output of a blower—a wooden box with interior partitions, channels, and insulation to interrupt the rotary action of the air and quiet the noise of the large-volume flow.
Another source of turbulence in organ wind is sharp turns in windlines. The eddy caused by an abrupt ninety-degree angle in a windline can be avoided by a more gradual turn or by the geometry of how one piece of duct is connected to another.
Air pressure drops over distance. Run a ten-inch (diameter) windline above the chancel ceiling from Great to Swell chambers and you’ll find that four inches of pressure going in one end becomes three-and-a-half inches at the other. Drop the diameter of the windline a couple times along its length (first to nine, then to eight inches for example) and the pressure doesn’t drop. As pressurized air and pressurized water behave in similar ways, you can see this principle demonstrated in many large public rooms in the layout of a fire-suppressing sprinkler system. The water pipes might be four inches in diameter at the beginning of a long run and step down several times, so the last sprinkler head has only a three-quarter inch pipe. It’s a direct inversion of the sliding doors in our house. When four big doors are open facing the wind and one small one is open at the other side of the house, all that ocean air gets funneled into racing down the corridor past the kitchen and out the back door. If you don’t prop the door open, it slams with a mighty bang.
We measure air pressure in “inches of water.” The basic gauge (called a manometer) is a U-shaped tube filled halfway with water. Water under the effect of gravity is the perfect leveling medium—when the U-shaped tube is half filled with water, the water level is exactly the same on both sides of the tube. Blow into one end, and the water on that side of tube goes down while the other side goes up. Measure the difference of the two water levels and you have “inches of water”—we use the symbol WP.
Many of the ratio-based measurements we use are two-dimensional. When we refer to miles-per-hour for example, all we need is a statement of distance and one of time. To measure pipe organ air we consider three dimensions. The output of an organ blower is measured in cubic-feet-per-minute at a given pressure—so we are relating volume to time to pressure. Let’s take a given volume of air. There’s a suitcase on the floor near my desk that’s about 24″ x 18″ x 12″. I make it to be three cubic feet. We can push that amount of air through a one-inch pipe at high pressure or through an eight-inch pipe at low pressure. The smaller the pipe and the higher the pressure, the faster the air travels. It doesn’t take much of an imagination or understanding of physics to realize that those two circumstances would produce air that behaves in two different ways.
A mentor gave me a beautiful way to understand the wind in a pipe organ—simply, that air is the fuel we burn to make organ sound. Put more air through an organ pipe, you get more sound. To get more air through an organ pipe, you can make the mouth (and therefore the windway) wider. A pipe mouth that’s two-ninths the circumference can’t pass as much air as one that’s two-sevenths. You can also increase the size of the toe hole and raise the pressure.
I’m not doing actual calculations here, but I bet it takes the same number of air molecules to run an entire ten-stop Hook & Hastings organ (ca. 3″ WP) for five minutes as it takes to play one note of the State Trumpet at the Cathedral of St. John the Divine in New York (ca. 50″ WP) for thirty seconds. Imagine trying to hand-pump that sucker. It was mentioned in passing that when that world-famous stop was being worked on in the organbuilder’s shop during the recent renovation of that magnificent organ, the neighboring motorcycle shop complained about the noise!
I’ve written a number of times in recent months about the project we’re working on in New York. Because it’s an organ with large pipe scales and relatively high wind pressures, we’re spending a lot of time thinking about proper sizes of windlines to feed various windchests. I use the term windsick to describe an organ or a portion of an organ that doesn’t get enough wind, as in, “to heal the windsick soul . . .”
This organ has a monster of a 16′ open wood Diapason that plays at both 16′ and 8′ pitches. The toe holes of the biggest pipes are four inches in diameter (about the size of a coffee can). If the rank is being played at two pitches and the organist plays two notes (say for big effect, lowest CCC and GGG), we have four of those huge toe holes gushing wind. If we might have as many as four of those big holes blowing at once, what size windline do we need going into that windchest? To allow for twice the flow of air do we need twice the diameter windline? Here’s pi in your eye. To double the airflow, we need twice the area of the circle, not the diameter. The area of a four-inch circle (πr2) is about 50.25 square inches. The area of a five-and-a-half inch circle is about 95 inches. The larger the circle, the bigger the difference. The area of a nine-inch circle is 254.5 square inches. Two nine-inch windlines equals 509 square inches. One twelve-inch circle is 452 square inches, almost twice the area of the nine-incher.
That Diapason plays on 5″ WP—a hurricane for each note.
You can use any liquid to make a manometer. We can buy neat rigs made of glass tubes joined at top and bottom by round fittings. A longer rubber tube is attached to a wooden pipe foot (such as from a Gedeckt). You take an organ pipe out of its hole, stick the foot of the gauge in the same hole, play the note, and measure the pressure. You can also buy a manometer with a round dial, which eliminates the possibility of spilling water into a windchest—heaven help us. Measuring to the nearest eighth-inch, or even to the nearest millimeter, is accurate enough for pipe organ wind pressure. But using a denser liquid allows for more accurate measurement.
A barometer is similar in function to a manometer, except that it measures atmospheres instead of air pressure. Because the difference between high- and low-pressure areas is so slight, mercury (the only metal and the only element that’s in liquid form in temperate conditions) is commonly used in barometers. The unit of measure is inches-of-mercury (inHg); 29.92 inHg is equal to one atmosphere. Right now, right here, the barometer reading is 29.76 inHg. According to my dictionary, the record high and low barometric readings range from 25.69 inHg to 32.31 inHg. I guess today we’re pretty close to normal.
Measuring and reading barometric pressure takes us back to my eagles and hawks. An updraft creates a low-pressure region, which is filled by air rushing in from areas of higher pressure. That’s how wind is made. Wind doesn’t blow, it’s just lots of air running from one place to another.
On July 4, 2002, Peter Richard Conte played Marcel Dupré’s Passion Symphony on the Grand Court Organ of Philadelphia’s Wanamaker (now Macy’s) Store as a special feature of that year’s convention of the American Guild of Organists. It was an evening performance, and the store’s display cases were moved aside to allow for concert seating. This was early in the great rebirth of that singular instrument, and organists and organbuilders were thrilled by its majesty. Dupré conceived this monumental work of music as an improvisation on the Wanamaker Organ in 1921. (You can purchase the live recording of Conte’s performance from Gothic Records at <http://www.gothic-catalog.com/The_Wanamaker_Legacy_Peter_Richard_Conte_…;.)
The last minutes of that piece comprise a barrage of vast chords, chords that only a monster pipe organ can possibly accomplish. When I hear an organ doing that, I picture thousands of valves of all sizes flying open and closed and the almost unimaginable torrent of air going through the instrument. I remember thinking (and later writing) that as Conte played the conclusion of the symphony, barometers all across New Jersey were falling. Must have been some eagles soaring above the store. 

Since 1968, Francesco Ruffatti has been a partner, along with his brother Piero, of Fratelli Ruffatti—Ruffatti Brothers Family of Artisans—of Padova, Italy. The firm is involved in the restoration of historic organs and the construction of new pipe organs, and has worked for decades in Italy and many other countries, including the United States, Canada, South Korea, Japan, Australia, Mexico, and Sweden. Francesco Ruffatti holds the position of tonal designer with the company. He supervises the design of construction parameters of the pipe stops and their voicing. He is involved directly in the study, cataloguing, and restoration of voicing, and researching the temperament of the pipework of ancient organs undergoing restoration. He has co-authored several publications and has written articles in this area of expertise for both Italian and American journals, including “Gaetano Callido, Organbuilder in Venice,” The Diapason, December 1998, and “The Historical Italian Organ—Tradition and Development,” The Diapason, June 2001. He has also participated as a speaker at numerous conferences. A two-term past president of the Association of Italian Organbuilders, Francesco Ruffatti is currently teaching restoration practices and the theory and practice of flue and reed voicing at the school for organbuilders of the Lombardy region in Crema, Italy. Fratelli Ruffatti is a member of both the Association of Italian Organbuilders and the International Society of Organbuilders. Judit Angster comes from the famous Hungarian organbuilder family Angster. She holds a Diploma and PhD in physics. Since 1986, she has been engaged primarily in pipe organ research. Since 1992, she has been working for the Fraunhofer Institute (IBP) in Stuttgart, Germany, as head of the “Research Group of Musical Acoustics,” where, among other things, important European research projects were carried out in close cooperation with organ building companies. From 1994 until 2003, she taught classes in acoustics for master craftsman courses (the highest level of education and training) for organ building at the Federal College of Organ Building in Ludwigsburg, and intensive advanced training courses for pipe organ and church acoustics at the Fraunhofer Institute (regular workshops for further education of organ experts). She also lectures in acoustics at the University of Stuttgart and at the University of Music and Fine Arts in Stuttgart. Dr. Angster is President of the Technical Committee of Musical Acoustics of the German Society of Acoustics (DEGA) and a member of the Executive Board Council of the German Society of Acoustics (DEGA). She is the author of 115 publications in scientific/technical journals, conference proceedings, etc., ten patents, one book, 113 invited papers for conferences, congresses and at different institutes and societies.

The organbuilder’s viewpoint
Investing in research is foreign to most organbuilders. The pipe organ is a traditional instrument, for which it is natural to think that everything has already been invented. Research is therefore perceived by most as something that has no value, since no advancements can be made. The possible exception to this involves the console systems and controls, where conservative attitudes in many cases have been overwhelmed by the very practical need of many organists to have tools on hand that can facilitate their performances. But what about sound, and the very principles that control the ancient art of voicing? In such areas, one will find that every single pipe voicer thinks that his way is the way it should be done, and procedures cannot be improved upon from his normal practices.
Voicing is largely a matter of taste, and subjective preferences are the only governing factors. Very often, an organbuilder is chosen because of the sound that his instruments produce, meaning essentially the stylistic approach to sound that he takes. Why would he then be interested in research in this field? Why change something that already works?
My entire career has been guided by two principles: anything can be improved upon, and an organbuilder never ceases to learn. The combination of these two beliefs has determined my personal desire to take part in scientific research programs. For almost a decade, Fratelli Ruffatti has participated in joint European projects aimed at finding ways to improve the art of organbuilding. Such projects have determined the need to conduct a great deal of fundamental research, which has been carried out over the years by a number of notable institutions, among which are the Fraunhofer Institut für Bauphysik (IBP) in Stuttgart, Germany, the University of Edinburgh, the University of Prague, the University of Budapest, and the Steinbeis Transfer Center of Applied Acoustics in Stuttgart. The Fraunhofer IBP in particular has been the constant guide and the main force behind fundamental and applied research.
The programs have been encouraged and co-sponsored by the European Commission in Brussels. A small group of organbuilders,1 coming from different European countries, participates in the research investment and actively cooperates with the scientists. Astonishing results have been obtained over the years, ranging from more efficient and silent wind systems, to efficient ways to evaluate room acoustics and to better adapt pipe organs to different acoustical environments. Recently, a revolutionary wind system has been invented, a monumental advancement over the traditional winding methods, which allows the organbuilder to simply avoid the use of reservoirs, schwimmers or related equipment, while at the same time obtaining unprecedented stability and efficiency in the wind supply of pipe organs.
The research currently under way deals with sound. The aim of this two-year process is to find better ways to reduce or eliminate problems that exist both in the field of “scaling,” or pipe dimensioning, and in “voicing,” meaning the process by which the pipes are given their proper sound character. At first sight, one may think that a project of this nature is aimed at “standardizing” organ sound by promoting uniform procedures for all. This is not at all the case. The idea is to provide scientific, undisputable knowledge, which can be used by each organbuilder to better reach his individual tonal ideals. Examples are the application of scientific principles to calculate an efficient shape for large wooden pipes that will make them prompt in their attack despite their size, while ensuring the production of the needed fundamental. Other interesting examples under research are finding practical ways to make the transition between stopped and open pipes, or the transition between wooden and metal pipes within one single rank, as tonally undetectable as possible.
In such a research program, the subject of voicing techniques could not be avoided. Once again, the objective was not that of teaching new ways to voicers with decades of experience, but to find out scientific evidence in a field that has never been properly analyzed with scientific methods, with the purpose of supplying new knowledge that the voicers will then use at their discretion and according to their personal taste.
One of the steps that has been analyzed concerns the investigation of the differences between the practices of open-toe and closed-toe voicing. Open-toe voicing is a technique by which flue pipes are voiced with their toe hole completely open, thus achieving continuity between the size of the toeboard hole and that of the pipe foot. With this technique, the pipe toe opening is not used to control the volume of sound that the pipe produces. On the other hand, with the technique called “closed-toe voicing” the volume control in the pipe sound is achieved by means of adjusting the diameter of the pipe toe opening.
It is the opinion of many that the difference between the two techniques merely represents a choice in the method for controlling the sound volume of pipes and that there are few and marginal effects on the quality of sound. If the volume can be well equalized by closing the pipe toes, why choose to avoid such practice? Even the first, partial results of the investigation are proving that such an assumption is an oversimplification. The two methods produce different tonal results, which can be detected and measured.
An experimental session was called in April 2009 at the Fraunhofer Institute in Stuttgart. The participants spent two solid days investigating a number of metal pipes specially built for the experiment. The research took place in a very sophisticated structure: a huge anechoic room of almost 2,000 cubic meters in volume. The test “floor,” a steel grille placed at mid-height (20 feet from floor level), housed the several people involved in the experiments, plus all of the needed equipment: sophisticated pressure sensors (along with a less sophisticated old-fashioned wind gauge), computers, sound pressure detectors, state-of-the-art microphones, etc.
The group of researchers included Dr. Judit Angster, head of the Research Group of Musical Acoustics and Photoacoustics of the Fraunhofer IBP; Prof. Andras Miklos, director of the Steinbeis Transfer Center of Applied Acoustics and a world-famous researcher in the field; Johannes Kirschmann, voicer and restorer of the firm Mühleisen of Leonberg, Germany; Francesco Ruffatti, tonal director and head voicer of Fratelli Ruffatti of Padova, Italy; and Thomas Trommer and Maria Cabanes Sempere, scientists at the Fraunhofer IBP.
During this intensive session, two sets of pipes, one of Principal scale and one of Open Flute scale, were analyzed. Each set was made of four identical pipes, two of them voiced with the open-toe and two with a controlled-toe opening. To reduce the risk of subjectivity, each voicer worked on and prepared one open- and one closed-toe pipe. The same procedure was repeated at three different wind pressures, ranging from 70 mm water column, just slightly less than 3 inches, to about 170 mm, or slightly less than 7 inches. Pipes were voiced with no nicking at the languids, but further investigations were carried out also with nicked languids in different configurations. All pipes in each set and for each trial were voiced to equal, instrumentally measured sound volume.
The wind pressure was measured not only inside the windchest but also inside the pipe toes of both the open- and closed-toe pipes.2 The sound of each pipe was also recorded simultaneously but separately at both radiating points, i.e., at the mouth and at the top of the resonator. In addition, the “mouth tone”3 was also recorded from each pipe at each step.
A huge quantity of data was collected, which is currently being analyzed. During the test session, however, several interesting phenomena could already be observed. 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%. A further immediate difference was detected in open- versus closed-toe pipes: 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 the wind noise, and this in turn will determine significant modifications to the structure of their sound.
The final results will be presented, with scientific data and measurements, to the project participants in the near future. These are occasions where the various organbuilders share experiences and learn from the scientists, an invaluable help to modern organbuilding.
—Francesco Ruffatti

The scientist’s viewpoint
Organ building is a traditional craft, which entails a valuable body of knowledge passed from generation to generation and which therefore should be preserved. Nevertheless, innovative design methods and technologies can be applied in the daily practice of this craft in order to optimize the design and production of organs, without endangering the valuable traditions inherent to their fabrication. The organbuilding firms that are taking part in the European research projects recognize that the quality and the effectiveness of their work can be considerably enhanced by adopting scientific and technological innovations into their craft.
In the current pipe project, before starting applied research, it was necessary to carry out fundamental research to reach a better understanding of the physics of flue pipes in organs. Furthermore, some special tools had to be developed, including special software for the analysis of pipe attack and stationary sound. The measurements were carried out in the anechoic room of the Fraunhofer IBP, where an acoustic-free field could be achieved. Here the pipe sound can be detected without any acoustical influence from the surrounding space.
The pipes were positioned on a functioning model windchest. All the other parts of the wind system, like reservoir and blower, were set outside of the room so that the sound detection would not be disturbed by any noises (Figure 1). The sound of individual pipes was detected by changing parameters one at the time, in order to evaluate the physical effect of single voicing steps. The evaluation of the experimental results is currently being carried out with the help of the above-mentioned special software.
The selected flue pipes that are the object of the research are being analyzed from the standpoint of the physical features of their steady sound spectrum and of the analyzed onset of the sound. A stationary spectrum of a flue pipe can be seen in Figure 2. This spectrum shows the most important properties of the sound of flue pipes, some of which are listed as follows:
1. A series of harmonic partials. As is well known from the elements of the Fourier theory in mathematics, any periodic signal has a lined spectrum with several harmonic partials and mostly a complicated spectral envelope.
2. A second series of smaller and wider peaks, which are not harmonically related, but slightly stretched in frequency—these peaks are at the frequencies where the sound will be amplified by the pipe body (acoustically called pipe resonator).
3. A frequency-dependent base line—this is the characteristic noise spectrum of the air flowing out of the flue.
An example of attack transient of an organ pipe of the Diapason family can be seen in Figure 3. Three phases can be subjectively distinguished in the attack of flue pipes.1 These parts cannot be entirely separated in time because they overlap quite broadly. Therefore, it is better to refer to them as three components, which start almost simultaneously, but develop at different rates. These three components can be characterized as follows:
• Forerunner. This is the sound heard first. It is very difficult to describe. It may have a pitch, but sometimes no pitch can be assigned to it. Several different terms are used for this component, such as chiff, ping, hiss, cough, etc.
• Appearance of a pitch. The second component in the attack usually has a pitch close to the pitch of a higher harmonic partial. This component is very important for certain stops. For example, for several diapason stops the second or the third harmonic can be heard preceding the fundamental.
• Onset of the fundamental. The third parameter of the attack is the rise time of the fundamental. For stops of the flute family, this rise time is very short, whereas it is very slow for stops of the string family. As the fundamental grows, certain components of the attack simultaneously become weaker.
The presence of the first two components is not compulsory in the attack. Moreover, the voicer can seriously influence the attack by producing, according to his taste, a faster or slower speed, a more or less pronounced forerunner, brighter or more fundamental sound, etc. It is worth mentioning that sometimes one or more partials are quite strong at the beginning of the attack, but become weaker in a later phase of the development of sound. The measurements show that the perception of the attack can be assigned to measurable properties.
The three parts of the attack can be clearly detected in Figure 3. The forerunner appears in every partial, implying its broadband nature (chiff). Then the partials start to grow; the fastest component is the sixth one. After a while, the second will be the strongest; it dominates the attack in the 35–40 milliseconds domain. The fundamental slowly overtakes the second, which becomes slightly weaker as the fundamental rises.
It can be assumed that the presented characteristics of the attack in flue pipes are related to the basic physical properties of the pipes. These relations will be investigated also in the case of voicing with open and closed toe. In Figure 4 another three-dimensional representation of an analyzed onset (attack transient) of a flue pipe is shown. In this case also the time function of the noise between the partials can be observed.
One of the many tasks of the project is the investigation of the advantages and disadvantages of the voicing methods with an open-toe and with a controlled-toe opening. In doing so, an aspect that has been analyzed from a scientific viewpoint deals with the radiated sound power (“volume of sound”) as a physical parameter.
The values of the pressure and flow are indifferent from a physical point of view, since the same sound power can be achieved by
• large foot pressure and small flue area (voicing by open toe)
or by
• small foot pressure and large flue area (voicing by closed toe).
The sound power depends on the air volume, which is proportional to the flue area and to the square root of the wind pressure in the toe. The pressure in the foot is constant in the case of an open toe; consequently there is only one parameter, the flue area, which can be varied by the voicer. By closed-toe voicing, the wind pressure in the foot can be changed, e.g., in this case two parameters can be set: the wind pressure and the flue area.
There is one more difference that must be mentioned. In a closed-toe pipe, a cross-sectional jump in the flow occurs at the foot hole through which flow noises can be generated. As the measurement results show in Figure 5, the noise level in the pipe sound is lower in the case of voicing with an open pipe foot.
The above are only a few and partial examples of the thorough investigation that is being carried out to evaluate the different aspects and characteristics of the open-toe and closed-toe voicing methods. Their influence on the attack transients will also be investigated.
A great advancement in the research process has come from technology that allows one to see the air flow pattern at the pipe mouth. A plexiglass “window” was created in the pipe, and air mixed with smoke was utilized to activate the pipe. By means of sophisticated equipment, involving a laser light source and a high-speed camera, it has been possible to film the movement of the air flow (see illustrations). The process is the work of scientists Hubert Ausserlechner, Fraunhofer Institute for Building Physics (IBP), Stuttgart, and Margit Liehmann, Fraunhofer Institute for Chemical Technology (ICT), Pfinztal.
In addition to the subject above, the research program has already produced excellent results in examining wooden pipes, open and stopped, of different shapes, with the aim of scientifically calculating the best shape from the standpoint of the efficiency of their air column. In addition, specific research will be aimed at finding efficient solutions for the tonal transitions between stopped and open pipes, or between pipes of different shapes and materials within the same rank. This is not an easy task, but a very exciting one, which can bring immediate and tangible results to the day-by-day work of the organbuilders involved in the research.
—Judit Angster

Common reference projects for cooperation for both authors—European CRAFT (Co-operative Research Action For Technology) projects within the framework of Brite-Euram III program:
1. “Development and Modernization of the Wind Supply Systems of Pipe Organs“ (BRST-CT98-5247)
2. “Advanced Computer Designed Open Wind Systems for Pipe Organs” (G1ST-CT2001-50139)
3. “Development of an innovative organ pipe design method” (G1ST-CT-2002-50267)
4. “Innovative Design Method for Matching the Pipe Organ to the Acoustics of the Room” (COOP-CT-2005-017712)
5. “Innovative Methods and Tools for the Sound Design of Organ Pipes” (FP7-SME-2007-1, Research for SMEs – 222104) (current project)

Shifty and puffy

It is mid-September in mid-coast Maine, and the days are getting shorter. Sunset here is about sixteen minutes earlier than in New York City, as we are as far east as we are north of the Big Apple. There are four windows facing east in our bedroom that allow us to track the motion of the sun, which is rising further south than it did a month ago. When we are on the water, we notice that the afternoon sun is lower in the sky as the sunlit water sparkles differently than in the height of summer. And the wind changes dramatically with the change of season. In mid-summer, we cherish the warm sea breeze, predominant from the south or southwest, caused by the air rising as it crosses the sun-warmed shore. All that cooler air above the ocean rushes in to fill the void, and we can sail for miles without trimming the sails in the steady and sure wind.

We had our last sail of the season last weekend in lumpy, bumpy wind from the northwest, which is never as steady as the southwesterlies. It is shifty and puffy, and it can be a struggle to keep the boat going in a straight line. Just as you get going, you get “headed” by a burst of wind from straight ahead, or you get clobbered abeam by a twenty-five mile-per-hour gust. Oof.

You have read this kind of thing from me before, thinking about sailboats when I should be writing about pipe organs, but because both are important parts of my life, and both involve the management of wind, I cannot escape it. And I am thinking about it a little more than usual because at the moment I am releathering three regulators for the organ I am working on. My method for assembling and gluing the ribs and frames of a wind regulator involves seven steps:

• Glue outside belts on the pairs of ribs.

• Glue inside canvas hinges on the pairs of ribs.

• Glue canvas hinges around regulator frames and bodies.

• Glue ribs to top frames.

• Glue ribs/top frames to body.

• Open regulator and glue gusset bodies.

• Close regulator and glue gusset tails.

It is still officially late summer as I write this, and my personal workshop is a three-car garage. Since we are on the shore, I love to have the overhead doors open to the breezes, though it is humid here. I am using the traditional flake hide glue (the stuff that is made when the old horse gets sent to the glue factory) that you cook in an electric pot with water, apply hot, and wipe clean with a hot-water rag that I keep just hot enough that I can put my hands in to wring the rag dry in the sort of double-boiler from which you scoop oatmeal at a cafeteria line. For the glue to set, the moisture must evaporate, and since the air is humid, I have to wait overnight between each step. Running fans all night keeps the humidity down and speeds the drying. In winter, when the air inside is dry, I can typically do two gluing steps in a day.

One of the regulators I am working on is thirty inches square. For that one I am using around twenty-five feet of one-inch-wide heavy canvas tape for the hinges and a comparable length of laminated rubber cloth for the outside belts. The gussets (flexible leather corner pieces) are cut from supple heavy goat skins that have a buttery texture and are impossible to tear. The key to finishing a wind regulator is finding a combination of materials that are all very flexible and strong, that are easy to cut, and that receive glue well enough to ensure a really permanent joint. If the structural integrity of a regulator is iffy, the wind will be shifty and puffy, and it will be a struggle to keep the music going in a straight line. Just as you get going, you get “headed” by a burst of wind that jiggles the music, or you get clobbered by a jolt from out of nowhere.

What’s in a name?

I am referring to these essential organ components as “regulators.” We also commonly call them “bellows” or “reservoirs.” All three terms are correct, but I think regulator is the most accurate description of the function of the thing. Taken literally, a bellows produces air. Air is drawn in when it is opened and pushed out when it is closed, like the simple bellows you have by the fireplace. The hole that lets the air in is closed by an internal flap when air is blown out.

A reservoir stores air. In an organ built before the invention of electric blowers, it was common for an organ to have a pair of “feeder bellows” operated by a rocking handle that blew air alternately into a large reservoir. The feeders had the same internal flaps as the fireplace bellows. The top of the reservoir was covered with weight (bricks, metal ingots, etc.) to create the air pressure, and the air flowed into the organ as the organ pipes consumed it. The bellows were only operated, and the reservoir was only filled when the organist was playing. Just try to get that kid to keep pumping through the sermon. . . .

With the introduction of the electric blower, it became usual to turn the blower on at the beginning of a concert or service and leave it running. That made it necessary to add a regulating valve between the blower and the reservoir. When the reservoir filled and its top rose, the valve closed, stopping the flow of air from the blower, so the system could idle with the blower turning and the reservoir full. When the organist played and therefore used air, the top of the reservoir would fall, the valve would open, and the air could flow again. Like before, there was weight or spring pressure applied to create the proper wind pressure. The addition of that valve added the function of pressure regulation to the bellows. In an organ with an electric blower, the bellows are storing and regulating the pressurized air. Calling it a regulator seems to cover everything.

The longer you go, the heavier you get.

Twice in my life, I have heard EMTs comment about my weight when lifting the stretcher, once after a traffic accident in the 1970s, and again after a fall in an organ seven years ago. But that is not what I am talking about here. We usually think of an inch as a unit to measure length or distance, so how can it refer to pressure, as in, “the Swell division is on six-inches of pressure?”

In industrial uses of pressurized air, more familiarly, in the tires or of your car, the unit of measure is pounds per square inch (PSI). I inflate the tires of my car to 35 PSI, and I use 80 or 100 PSI to operate pneumatic tools. But while my workshop air compressor gauges those high pressures, the actual flow is pretty small, something like two cubic feet per minute.

Organ wind pressure is much lower, and we measure it as “inches on a water column.” Picture a clear glass tube in the shape of a “U” that is twenty-inches high. Fill it halfway with water, and apply pressure to one side of the U. The water goes down on that side of the tube, and up on the other. Use a ruler to measure the difference, and voilà, inches on a water column, or centimeters, or feet. You can easily make one of these using plastic tubing. The little puff it takes to raise three inches of pressure is just the same little puff it takes to blow an organ pipe you are holding in your hand. Instead of the actual tube full of water, we use a manometer that measures the pressure on a gauge without spurting water onto the reeds.

Did you ever wonder how the conversion works? One PSI equals almost 28 inches on a water column. Five inches on a water column equals about .18 PSI. And how does that relate to the organs you know? In a typical organ, it is usual to find wind pressures of three or four inches. In general, smaller organs with tracker action might have pressures as low as forty millimeters, or less than two inches. In a three-manual Skinner organ, the Great might be on four inches, the Swell on six, and the Choir on five. In a big cathedral sized organ, solo reeds like French Horn and English Horn might be on fifteen inches, while the biggest Tubas are on twenty-five. The world-famous State Trumpet at the Cathedral of Saint John the Divine in New York City is on fifty inches (incredible), and in the Boardwalk Hall organ in Atlantic City, New Jersey, the Grand Ophicleide, Tuba Imperial, Tuba Maxima, Trumpet Mirabilis are on one hundred inches of pressure, or 3.61 PSI! Stand back. Thar she blows!

Once you have determined pressure, you also have to consider volume. A twenty-rank organ at three inches of pressure might need 1,000 cubic feet per minute at that pressure to sustain a big chord at full organ. Some of the largest organ blowers I have seen are rated at 10,000 CFM at ten inches of pressure. And when you lift the biggest pipe of a 32′ Open Wood Diapason and play the note as an empty hole, you will blow your top knot off. It takes a hurricane coming through a four-inch toehole to blow one of those monster organ pipes.

All the air you could wish for

Before the introduction of the electric blower, most organs had at least two bellows. One would be in free fall, supplying pressure to the organ while the other was raised by the organ pumper. The system I described earlier with two feeders and a reservoir was a great innovation, because once the reservoir was full, the pumper could slack off a little if the organist was not demanding too much wind. The six-by-nine-foot double-rise reservoir in the heart of a fifteen-stop organ by E. & G. G. Hook or Henry Erben has huge capacity, and can blow a couple 8′ flutes for quite a while without pumping. Organs by Hook are great examples of efficiency, with pipes voiced in such a way as to produce lots of tone with very little air, and even large three-manual organs are pumped by just one person using the two-feeders-and-a-reservoir system.

The electric blower changed everything. Organbuilders and voicers could now work with a continuous flow of wind at higher pressures than were available before. New styles of voicing were invented, and along with the introduction of electric keyboard actions, organs could be spread around a building, creating stereophonic and antiphonal effects. When organs were first placed in chambers, and their sounds seemed remote, the builders raised the pressure and increased the flow of air through the pipes, driving the sound out into the room.

While modest organs with electric blowers usually have only one wind regulator, larger instruments can have dozens. In a big electro-pneumatic organ, it is common to have a separate regulator for each main windchest. That is how Ernest Skinner could have the various divisions of an organ on different wind pressures, as each individual regulator can be set up to deliver a specific pressure.

But what about wiggly?

When I mention factors that can add to the stability of an organ’s wind system, I raise the question about “wiggly wind,” or “shaky wind,” both somewhat derogatory terms that refer to the lively flexible wind supplies in smaller and mid-sized mechanical action organs with lower wind pressure. When wind pressure is low and an entire organ receives its air from a single regulator, the motion of the wind can be affected by the motion of the music. It is especially noticeable when larger bass pipes are played while smaller treble pipes are sustained. At its best, it is a delightful affect, akin to the natural flow of air through the human voice. At its worst, it is a distraction when the organ’s tone wobbles and bounces.

This phenomenon is part of the fierce twentieth-century debate concerning “stick” organs versus so-called “industrial-strength” electro-pneumatic organs. I have been servicing organs for more than forty years, and I have often thought that much of the criticism of the emerging tracker-action culture was because craftsmen were reinventing the wheel, learning the art of organbuilding from scratch. They may have measured the dimensions of an organ bellows accurately but failed to compensate for the fact that the ancient model did not have an electric blower. And let’s face it: a lot of flimsy plywood tracker organs were built in the 1960s and 1970s, enough to give that movement a bad name from the start.

The evolution of modern tracker organs toward the powerful, thrilling, reliable, sonorous instruments being built today has much to do with how much the craft has learned about the management of wind over the years. A little tracker organ built in 1962 might have key channels and pallets that did not have the capacity to blow their pipes. It might have flexible wind conductors to offset bass pipes that were too small and that jiggled when the notes were played, causing the tone to bounce. It might have bass pipes with feet that were too short, so air did not have a chance to spread into a dependable sheet before passing between the languid and the lower lip. All of these factors affect the speech of the pipes, giving the impression that the organ is gasping for air. And worse still, you might hear the pitch drop each time you added another stop. I have worked on organs where adding an 8′ Principal made the 4′ Octave sag. How do you tune a thing like that? I marvel now at how air pressure moves through the best new tracker organs, especially at the wonderful response of large bass pipes. Organs by builders like Silbermann do not lack in bass response. Once the revival movement was underway in the middle of the twentieth century, it took a few decades to really start getting it right.

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The organ I am working on today is a simple little thing with two unit action windchests. Each has its own regulator, and there is a third “static” regulator that mounts next to the blower. The blower produces seven inches of pressure; the static regulator brings it down to five inches and distributes the wind to the other two regulators, which each measure out four inches. The biggest pipes in the organ are the 16′ Bourdon, and though there are only ten ranks, it is a unit organ, and a lot of pipes can be playing at once. It is destined to be a practice instrument for a university organ program, so I know that talented and ambitious young organists will be giving it a workout as they learn the blockbuster literature we all love so much. I hope that those students never have to worry about having enough air. And perhaps Maine’s salty breezes will travel with the organ, adding a little flavor to the mix.

C. B. Fisk, Inc.,
Gloucester, Massachusetts
First Presbyterian Church,
Santa Fe, New Mexico

From the organbuilder
Since its incorporation in 1961, the Fisk workshop has been in Gloucester, Massachusetts, home of the oldest art colony in the United States. Just as artists have been drawn to the light and ocean-
scapes of Gloucester for decades, so have they been drawn to the desert light of Santa Fe. Thus, when C. B. Fisk received a letter in 1999 requesting a proposal for a pipe organ in the sanctuary of the First Presbyterian Church, we were especially excited by the opportunity to work in the Southwest, with its own quality of light and architectural styles so different from those surrounding us in our New England home.
From our first visits to John Gaw Meem’s serenely beautiful 1930s sanctuary, it was evident that there were wonderful opportunities and challenges inherent in the project. When plans were made to restructure the chancel as part of a larger building project, the church wisely included us along with acousticians Kirkegaard & Associates, and architects Lloyd & Associates. The excellent result literally speaks for itself. While maintaining the simple beauty of the space, a modern approach to acoustics was applied. The walls at the chancel sides are now hard-plastered and subtly angled, allowing choir and organ to speak boldly into the sanctuary. Other changes were made invisibly above the ceiling in the sanctuary, leaving the latillas undisturbed, but improving the acoustical response so important to congregational singing. This commitment to the excellence of both sound and silence will pay dividends for generations to come.
Our first step was to take careful measurements and photos of the new chancel in order to construct a scale model of the front of the sanctuary. Much research was done on the vernacular church architecture of the Santa Fe area, with special attention to the surrounding historic missions. Charles Nazarian then developed the visual design within the model in consultation with the Fisk design team and the organ committee, whose members visited Gloucester several times throughout the process. Designing in the model also gave us the opportunity to communicate with the organ committee and the congregation through digital photography sent via e-mail.
The organ façade serves as a liturgical reredos and is divided in three—the detailed central case flanked on each side by the Douglas fir pipes of the 16′ Contrebasse. The painted casework is constructed of solid poplar, and the console of cherry. Both feature joinery designed for a dry climate. The casework and the wooden front pipes were hand-planed, providing a texture consistent with the hammered lead pipes in the central tower and the hand-carved spiral posts that support it. Great care was taken to choose materials, decorative elements, shaping and colors to create an organ design unlike any other, yet appearing to have always been there.
The mechanical design of a tracker organ must be as simple and as direct as possible in order to increase an organ’s utility and reliability, and to allow an unfettered transmission of musical expression. The active musical life in Santa Fe all but guarantees that the organ will be played often, calling for the highest levels of care and attention to detail in its design and construction. Our experience with creating light, responsive actions and our increasing use of modern materials such as carbon fiber have made Opus 133 a new standard of key action touch.
Rooted firmly in historic principles, the tonal design is a unique blending of elements chosen specifically to meet the musical needs of the church. Dr. Larry Palmer of Southern Methodist University and Dr. Linda Raney, music director, consulted closely with us over a period of several years. The final stoplist is the result of careful research and thoughtful discussion in many areas of importance—the musical requirements of the Presbyterian liturgy, including leadership and accompaniment, the acoustics of the church, and the breadth and flexibility needed in a recital instrument.
The Great division is largely Germanic in nature, with most of its stops based upon our research trips to study the best 18th-century examples of organbuilding. The Great chorus, among its other duties, is designed to support congregational singing. The Swell division, by contrast, takes its character from 19th-century French examples, and is perfectly designed and balanced to accompany the choir and instrumentalists. The Solo division on the third manual can be used to enhance a hymn melody and creates the greater flexibility needed to play a wide selection of the entire organ literature.
The organ’s 2,065 pipes were pre-voiced at our Gloucester workshop and then each pipe was meticulously adjusted on site in Santa Fe. This tonal finishing process took place over the course of five months beginning in the spring of 2008, as the voicers refined the individual voices of the organ and balanced the overall sonority with the acoustics of the sanctuary. Because of the altitude and thinner air of Santa Fe, special voicing techniques and a larger blower were required to help the pipes speak with a full tone. The temperament is the mildly unequal Fisk II, which, while favoring the common keys, allows for music of all styles to be performed. Wind pressures are 3 inches water column for the manual divisions and 4¾ inches for the Pedal.
C. B. Fisk wishes to thank the staff and congregation of First Presbyterian Church for the opportunity and privilege of building an organ in their remarkable and inspiring church. Without the constant support and hospitality of Dr. Raney, the members of the choir, and the organ committee, the pursuit of our art and our sojourn in Santa Fe would not have been half so rewarding and enjoyable.
—Gregory Bover
Project Manager

C. B. Fisk, Inc., Opus 133
First Presbyterian Church,
Santa Fe, New Mexico
29 voices, 31 stops, 41 ranks,
2,065 pipes

GREAT (Manual I)
16′ Bourdon
8′ Prestant
8′ Salicional
8′ Spillpfeife
4′ Octave
4′ Rohrflöte
2′ Superoctave
Mixture IV–VI
8′ Trumpet

SWELL (Manual II, enclosed)
8′ Violin Diapason
8′ Voix céleste (from C0)
8′ Stopped Diapason
4′ Prestant
4′ Flûte octaviante
22⁄3′ Nasard
2′ Octavin
13⁄5′ Tierce
Plein jeu IV
16′ Basson
8′ Trompette
8′ Hautbois

SOLO (Manual III)
8′ Harmonic Flute
Cornet V (from c1)
8′ Trumpet (from Great)
8′ Cromorne

PEDAL
16′ Contrebasse
16′ Bourdon
8′ Octave
8′ Bourdon (from 16′)
4′ Octave
16′ Posaune

Couplers
Swell to Great
Solo to Great
Great to Pedal
Swell to Pedal
Swell Super to Pedal
Solo to Pedal
Solo Super to Pedal

Controls
Tremulant
Wind Stabilizer
Balanced Swell Pedal

Key action: direct mechanical (tracker), except for certain large bass pipes
Stop action: electric with a modern multi-level combination action
Keydesk: 61 keys CC–c4, grenadilla naturals, rosewood sharps capped with cowbone; pedalboard: 32 keys CC–g1
Casework: a single case with façade pipes of wood and metal, standing in the front of the sanctuary, designed to harmonize with and adorn the historic Mission church interior