The Sound of Gottfried Silbermann, Part 2

December 22, 2022
Silbermann organ, Freiberg
1711–1714 Gottfried Silbermann organ, Freiberg Dom (photo credit: William Van Pelt)

Michael McNeil has designed, constructed, voiced, and researched pipe organs since 1973. Stimulating work as a research engineer in magnetic recording paid the bills. He is working on his Opus 5, which explores how an understanding of the human sensitivity to the changes in sound can be used to increase emotional impact. Opus 5 includes double expression, a controllable wind dynamic, chorus phase shifting, and meantone. Stay tuned.

Editor’s note: The Diapason offers here a feature at our digital edition—two sound clips. Any subscriber can access this by logging into our website, click on Magazine, then this issue, View Digital Edition, scroll to this page, and click on each <soundclip> in the text.

Part 1 of this series appeared in the December 2022 issue, pages 12–17.

Deductive logic is tautological; there is no way to get a new truth out of it, and it manipulates false statements as readily as true ones. If you fail to remember this, it can trip you—with perfect logic. . . . Inductive logic is much more difficult—but can produce new truths.21

A range of voicing styles

In Part 1 we discovered the features of Silbermann’s pipe construction and voicing that make his sound unique. What could we learn by comparing Silbermann’s voicing to other styles? A great deal, as it turns out, and to do this we will take a much deeper dive into the voicing parameters shown in Part 1.

Toe diameters

Toe diameters control power by limiting the flow of wind and reducing the pressure in the pipe foot. We often hear the term “open toe” voicing, but what does this really mean? And how could we compare the very different regulation of toes in Germanic and French voicing? Tables of raw pipe toe diameters do not convey the intent of the organbuilder or allow us to make meaningful comparisons. 

In 1972 Dirk Flentrop advised me that a starting point for estimating the diameter of a pipe toe is the square root of its resonator diameter, and that is assuredly not the widest possible toe.22 Building on this idea I devised what I call a toe constant “c” to compare the flow of wind through pipe toes. Flentrop’s advice, the square root of a pipe’s diameter, defines a toe constant “c” of exactly 1. Interestingly, the toe constant for Andreas Silbermann’s pipe shown in Figure 2 in Part 1 is 0.97, virtually identical to Flentrop’s guidance.

Toe constants can be larger or smaller to suit the acoustics and the power balances within a chorus, and they can vary for different levels of wind pressure. For example, if we want more power at the same pressure, we will use larger toe constants and larger toes, and vice versa for less power. If we want the same power at a higher pressure, we will use smaller toe constants.

The toe constant also needs to take into account the larger or smaller flows of wind needed by different mouth widths. Mouth widths are specified as a fraction of the pipe circumference. A 2⁄7-width mouth is wider than a 1⁄4-width mouth on the same pipe, and it will need a larger toe to feed more wind to the wider flueway of that mouth. I added a term to Flentrop’s advice (he typically used 1⁄4 mouth widths) to adjust the wind required to feed wider or narrower mouths. For example, Silbermann’s toe constants in Figure 8 (page 17) have values of 1 at 2′ pitch, but those values reflect toes that are larger in diameter than the square root of their pipe diameters—those toe diameters are adjusted proportionally larger to provide the extra wind needed by the flueways of Silbermann’s wider 2⁄7 mouths. Note 23 shows the very simple equation for calculating the toe diameter from the pipe diameter, mouth width fraction, and toe constant. 

The toe constant now allows us to visually compare the relative flow of wind among voicing styles and wind pressures for pipes of any scale or mouth width. While the term “open toe” is vague, the toe constant is quantifiable.

Silbermann adjusted the toes of the Freiberg Dom chorus in Figure 8 for more wind flow in the bass and treble. None of the toe constants are below Flentrop’s guidance of 1. The highest trebles at 1⁄8′ pitch have reduced wind flow, and we will soon see a very interesting explanation for this. 

Note the regularity of Silbermann’s toe constants. All pipes of the same pitch have the same toe constants and wind flow regardless of where they appear in the stops or the compass. The mixtures appear to have slightly larger toes, perhaps as a compensation for their slightly narrower scale, indicating that Silbermann wanted the same power from the mixtures but with the brighter timbre of their narrower scale. 

Such regularity is extremely rare, and it suggests that Silbermann calculated his toe diameters prior to voicing. These data also suggest the idea that he approached organ design from an inductive viewpoint, using data to infer the design rules with which he achieved his sound. Some might criticize this regularity, but we might also learn something from it. Let’s see how other builders controlled their pipe toes.

Figure 14 (page 14) shows the toe constants for a vast range of voicing styles, most of which represent 4′ Octave stops in the main manual division. All of these styles have toe constants entirely above a value of 1 except for two cases: the classical French voicing of the Isnards and the high treble of D. A. Flentrop’s example. 

The data in the pink line are from D. A. Flentrop’s 1977 organ at California State University, Chico, voiced on a low pressure of 66 mm. This organ was built at a time when all classical voicing was considered “open toe,” but readers may be surprised to see that Flentrop’s voicing does not remotely use the most open toes in Figure 14. He deviated from his guidance (the square root of the pipe diameter) as needed, extending above 1 in the bass and mid-range, and dropping below 1 in the highest treble. The acoustically dry concert hall in which the Flentrop resides is also the smallest of the acoustics in Figure 14. His wind pressure is the lowest in Figure 14, and this might suggest the use of the most open toes, but Flentrop was willing to restrain these toes for a more restrained treble power.

The data in the orange line are from Silbermann’s organ at Großhartmannsdorf on 90 mm pressure, and the data in light blue are from his organ at Reinhardtsgrimma on 70 mm pressure. Note that Silbermann uses much more open toes on lower pressure. The Großhartmannsdorf data is virtually identical to the toe constants at the Freiberg Dom in Figure 8, evidence that these toes may have been calculated to accommodate the similar wind pressures of these organs. 

The data in the dark blue line are from the 1774 Isnard organ at Saint Maximin on 83 mm pressure. Here we have mid-range toe constants that dip well below a value of 1, and with this visual graphic we can now see what is meant by “closed toes” in this French voicing example.

The individual data points in the pink boxes are from the 16′ Hauptwerk Principal in Arp Schnitger’s 1688–1692 organ at the Jacobikirche in Hamburg on 80 mm pressure, one of the largest acoustics in the Figure 14 examples.24 These are widely open toes, and they also compensate for the wind pressure drop that occurs in the conductors between the windchest and the pipe feet of these offset façade pipes. Principal pipes that sit on the windchest of the Schnitger organ have toe constants closer to those of Silbermann at Reinhardtsgrimma in the light blue line. All of the other pipes in Figure 14 from 4′ to ¼′ pitch sit directly on the windchest without pressure losses.

The data in the yellow line are from the 1863 organ by E. & G. G. Hook at the former Immaculate Conception Catholic Church in Boston. This Romantic organ is voiced on 76 mm pressure, and it may surprise readers to see that it has the most “open toe” voicing in Figure 14 for pipes sitting directly on the windchest. 

The toe constants in Figure 14 show us that all of these organbuilders adjusted the toe to regulate wind flow and power. The toe constant gives us the means to make meaningful comparisons.

Flueway depths

Flueway depths control power. Flueway data are essential for understanding organ sound, but they are exceedingly rare. Figure 15 shows how flueway depths are measured. Figure 16 shows flueway depths for the same pipes shown in Figure 14. Figure 9 shows the very deep flueways of the Freiberg Dom Silbermann.

The Flentrop data in the pink line in Figure 16 explore the lower limits of flueway depths with excellent musical effect on 66 mm pressure. Figure 17 shows the bright, harmonically rich, “instrumental” voicing of a Flentrop pipe from about 1980. In addition to the two obvious deeper nicks and the extremely light nicks in the middle of the counterbevel, note the unusual bold nicks placed at the far right and left sides of the flueway, the absence of ears, and the moderate cutup. Flentrop’s harmonically rich voicing contrasts with the much less bright vocale style of voicing.

The data in the yellow line from the Romantic Hook organ explore the upper limits of musicality. These pipes are voiced on 76 mm pressure with many bold nicks. The Flentrop and the Hook data give us some idea of the range of historic flueway depths.

The Silbermann flueways in the orange and light blue lines represent the range of Silbermann’s flueway depths for the range of pressures represented by these data. Note that at 90 mm of pressure at Großhartmannsdorf, Silbermann’s flueways are virtually identical to the flueways of the Freiberg Dom chorus in Figure 9, more evidence suggesting calculation of flueways for a specific wind pressure. The treble flueways are as deep as those found in the Hooks’ Romantic voicing.

It is interesting that Silbermann adjusted his flueways shallower at lower pressure and deeper at higher pressure, an unexpected relationship. Open flueways without bolder nicking have a breathy component to their sound, and Silbermann may have adjusted his flueways shallower in smaller, more intimate acoustics to minimize that effect. The high frequencies that characterize breathiness are absorbed by the atmosphere, and distance reduces their audibility in larger acoustics.

The restorers of the Isnard organ interestingly noted that the very generous flueways in the dark blue line were more “closed up” relative to typical French voicing. As we will later see, the Isnards appear to have adjusted their flueways and toes to achieve remarkable balances. 

The individual data points in the Figure 16 pink boxes are from Schnitger’s 16′ Principal on 80 mm pressure. These Schnitger flueways correlate extremely well to the deepest flueways used by Gottfried Silbermann. All of the illustrated Schnitger data were taken by Hans Henny Jahnn in 1925.

For those interested in Schnitger’s work, Figure 18 shows a subset of Jahnn’s original data (he took data on every pipe in this stop). The data in the pink font in Figure 18 are represented in Figure 16 by the pink boxes. 

The single pink triangular data point well below the Flentrop data at 1′ pitch is the razor-thin flueway of the neo-Baroque pipe illustrated in Figure 3 of Part 1; it is voiced on 65 mm pressure with a very low cutup. The data clearly show that this flueway does not remotely resemble any historic voicing style in Figure 16, and the reason for that brings us to cutups.

Cutups

Cutups (also known as “mouth height”) are often described as some fraction of the mouth width. While using a mouth width fraction with dividers to scribe preliminary cutup heights on upper lips has some practical value during voicing, it has been shown that the tonal effect of cutup has absolutely nothing to do with the width of the mouth.25

Cutups are adjusted to control timbre, and cutups will be higher for the same timbre at a higher level of power. We will get continuously less bright timbres as cutups are increased at any specific power. Cutups that are too low will cut the vortex in the flueway at too high a frequency for the resonator to quickly respond, and the fundamental will form more slowly.

Some neo-Baroque efforts to recapture historic voicing invoked a recipe where cutups were required to be ¼ of the mouth width and toes were vaguely required to be “open.” This recipe is a perfect example of an untested opinion based on deductive logic (which the author, too, naively embraced in his Opus 1).

Pipes voiced with deep flueways, wide-open toes, and low cutups will either screech with powerful harmonics or overblow to the octave on higher pressures. Closing the flueway takes away the strident screech, but it also strangles the power of the fundamental. Using the neo-Baroque recipe of wide-open toes and ¼-cutups, the voicer was forced to close the flueway to extremely small values. Without reducing the wind pressure, this was the only option left to the voicer. A typical compromise in this style of voicing allowed for some stridency in the timbre to preserve some modest power in the fundamental, and in this condition the pipe was often too close to overblowing. The result was the slow, gulping speech and thin fundamental so often heard in early Orgelbewegung movement voicing. 

The solution to this problem is by now quite obvious to the reader—adjust the toe and/or the flueway (according to your preferences) until the desired fundamental power is achieved, and then raise the cutup to get the desired timbre and prompt speech. If Silbermann had used ¼-cutups at the Freiberg Dom, the values of his Normal Scale mouth heights in Figure 10 would look identical to the values of his Normal Scale mouth widths in Figure 5. Unsurprisingly, Silbermann’s high cutups bear no relationship at all to his mouth widths. 

Figure 19 shows cutups for the same pipes shown in Figure 16. The data in the pink line are from the Flentrop organ voiced on 66 mm pressure. Cutups trend higher on higher wind pressures, depending, of course, on the regulation of toes and flueways. The Flentrop data represent the lowest wind pressure in this graph with a harmonically rich, restrained power in the smallest acoustic among these examples. The lower cutups of the Flentrop voicing are no surprise.

The data in the orange line are from Silbermann’s organ at Großhartmannsdorf on 90 mm pressure, and the data in light blue are from the Reinhardtsgrimma organ on 70 mm pressure. This is the same data we saw in Part 1 where Silbermann used higher cutups at higher wind pressures to maintain similar timbres. Again, it is no surprise that these cutups are higher than Flentrop’s lower pressure voicing. In Figure 19 the wind pressures appear just to the right of the data lines, and in the treble they progress smoothly from lower cutups on lower pressure to higher cutups on higher pressure.

The data in the dark blue line are from the Isnard organ on 83 mm pressure. The Isnard cutups follow the same wind pressure trend as the Silbermann data and lie mostly between them. We might expect the 83 mm pressure Isnard cutups to lie closer to Silbermann’s 90 mm cutups. Figure 14 tells you why they do not (hint: look at the Isnard toe constants and the implied pressure drop in the pipe feet).

The individual data points in the pink boxes are from the Schnitger example on 80 mm pressure. The treble cutups from 4′ pitch reflect significant power in this 16′ stop, as would be expected from its copiously winded toes and flueways in Figures 14 and 16

The data in the yellow line are from the Romantic Hook organ voiced on 76 mm pressure. The highest treble data lie just above Silbermann’s 70 mm pressure data as expected. But the bass and mid-range cutups are much higher than expected, and this reflects the higher bass power of a Romantic organ, a power fed by the largest toes in Figure 14 and the deepest flueways in Figure 16. The Hook does not have the highest wind pressure in Figure 19, but it is a good example of getting more power out of larger toes and deeper flueways (and bold nicking). 

Higher cutup with more wind gives us power, and a good example is the Pedal 32′ Bourdon at Saint Ignatius Catholic Church in San Francisco, California. This large room seats about 1,800 people, and as a 64′ resultant this Bourdon is able to cause visible vibrations in the pews at its 8 Hz pitch. It has a scale of 535 mm on the diagonal, a mouth width of 349 mm, a 4.0 mm flueway, a 100 mm toe, and it is winded on 203 mm (8 inches) pressure. The power of this pipe is reflected in its cutup of +20 HT (203 mm average, arched). This cutup is literally way off the top of the graph in Figure 19. You do not hear such a sound; you feel it. On his next visit to the Atlantic City organ, John Bishop might regale us with the cutup of the Pedal 32′ Contra Diapason on 20 inches of pressure!

Toe and flueway ratios 

Areas are more important in many ways than diameters and depths, and the ratio of the toe area to the flueway area strongly affects speech articulation (also known as “chiff”). Figure 20 shows these ratios for the same pipes in Figure 19. Figure 11 shows the ratios for Silbermann’s Freiberg Dom organ. 

Ratios larger than 1 mean that we are trending toward more “open toe” voicing, where a pipe’s toe area is larger than its flueway area. A ratio less than 1 means that we are trending toward more “closed toe” voicing, where the toe is smaller and will flow less wind than the flueway. Examples of pipes with ratios far below 1 with very closed toes feeding especially deep flueways are common in theatre organs on exceptionally high wind pressures.

Articulation provides percussive clarity to rhythm, but lower ratios will reduce articulation. Wind pressure builds more slowly in the foot with smaller toes, and a slower buildup of pressure will make articulation more gentle and less percussive. Ratios above 1 tend to accentuate more articulate speech, and this is why we hear more articulation with “open toe” voicing. Classical French voicing, with its closed toes, deeply open flueways, and lower ratios will have much less articulation than North German voicing and less response to the touch of the key. 

All of the pipes below 1′ in pitch in the entire Grand Orgue principal chorus of the Isnard organ at Saint Maximin originally had ratios so close to 1 as to suggest that it was a purposeful goal.26 It is an exception in classical French voicing with its more moderate flueway depths, and it exhibits gentle articulation. In this soundclip we hear the exquisite articulation of the Isnard Positif 8′ Montre in Louis Marchand’s Tibi omnes angeli. <soundclip 4>
From the middle of the compass to the high treble, the toe constants of this stop range from 0.6 to 1.2, and the toe/flueway ratios range from 0.7 to 1.8.27

In Figure 20 we see that Silbermann’s organ at Großhartmannsdorf has ratios that never drop below 1, and they closely parallel the French voicing of the Isnards. The ratios of the Freiberg Dom organ in Figure 11 on a similar wind pressure are virtually identical, and we might gain some insight from this data to explain why the toe constants in Figure 8 drop at 1⁄8′ pitch. The ratios in Figure 11 continue to rise right up to 1⁄8′ in pitch, and this means that the flueways in Figure 9 have increasingly more wind from the toes as the pitch rises. The toe constants at 1⁄8′ pitch in Figure 8 obviously drop in their relative flow of wind, but those toes are still feeding increasingly more wind to much smaller flueway areas (i.e., the flueway areas are dropping at a faster rate than the toe areas). This is very strong evidence that Silbermann was calculating toe and flueway areas. 

Silbermann’s lower pressure organs have much higher ratios, i.e., they are much more “open toe,” and the more unmolested examples tend to exhibit more articulate speech. This is why the Orgelbewegung, which prized clear articulation, emphasized “open toe” voicing on lower wind pressures. The movement got it partly right, that more open toes will emphasize articulation, but the factor that matters more is the ratio, not the diameter of the toe. D. A. Flentrop’s voicing does not have the most open toes in Figure 14, but with the most closed flueways in Figure 16, the Flentrop ratios are generally the highest in Figure 20, and the articulation of this Flentrop is very clear.

Arp Schnitger did not use heavy nicking. His ratios in Figure 20 are high in both bass and treble, and his more unmolested pipes have clear articulation.

Fine nicking will reduce articulation, but bold nicking will eliminate it in all conditions. (Nicks likely stabilize the formation and position of the vortex on the languid edge.) About 90% of the pipes in the Isnard organ have no visible nicks on their languids. Much of the very fine nicking occurs on the separate mutations, giving them a smoother legato as a solo voice.28 French Romantic voicing evolved from the deep flueways of Classical French voicing, and it employed bold nicking to achieve a smooth Romantic legato. Nicking also has the same effect as raising the cutup, and the sound is less bright after adding nicks, i.e., nicking permits lower cutups for the same timbre. The Hook ratios in Figure 20 are high, but the bold nicking of the Romantic Hook voicing completely suppresses its speech articulation.

While on the subject of Romantic voicing we should note that this style often employs a tuning device, known as a Reuter tuning slot, which greatly reduces articulation. The tuned length is achieved by cutting a slot into the pipe that does not extend to the top of the pipe. If you want clear articulation, pipes need to be cut dead length or fitted with tuning slides that extend to the top of the pipe. Anything that makes the tuned length of the pipe indeterminate will reduce articulation. Classical French façade pipes with extreme overlengths and multiple cutouts at their backs to achieve the correct pitch have little articulation, and this is consistent with their closed toe voicing style. Articulate Germanic voicing trends toward dead-length tuning, which is also typical of Silbermann’s work. 

Ears 

There are more details that affect voicing in more subtle ways that are not within the scope of this article, but we should address one of them: ears. Romantic and neo-Baroque voicing make consistent use of ears because they significantly increase the power of the fundamental by about 1.5 dB. This is not trivial, and it represents a scaling increase of three halftones. But ears also come at a price with a strong increase in the power of a few discrete higher harmonics, and the resulting blend is worse. The blend of pipes with high cutups and few harmonics will be less impacted by ears. The spectral data on the change in power and timbre caused by ears is shown in the author’s book.29

Classically inspired voicing

We can readily grasp the Silbermann brothers’ use of deep flueways from their exposure to French voicing. But the deep flueways of Arp Schnitger’s work shown in Figure 18 are unexpected. Schnitger may indeed have significantly reduced his flueways for a more restrained power in smaller acoustics, much as we see in the data for D. A. Flentrop’s organ, but this is speculation without data on unmolested pipes. The Steinkirchen organ is reportedly the least tonally modified of Schnitger’s organs, but Rudolf von Beckerath’s documentation of that organ lamentably omits the crucial toe diameters and flueway depths.30

Perhaps of more interest, Schnitger’s Germanic voicing is not considered vocale by some American organ builders who practice that style; it is considered an instrumental style with brighter harmonic richness more like that of D. A. Flentrop. The vocale voicing I have observed trends to more open toes, more closed flueways in modern work (and very deeply open flueways in some ancient examples), varying degrees of languid counterbevels, and very high cutups in both older and modern work. Vocale cutups tread in that range of timbres between a principal and a brighter flute.31 Subjective impressions suggest that vocale voicing cuts the vortex above the height where it spins at the frequency of the tuned resonator, i.e., above the point where Coltman’s impedances match and Ising’s fundamental forms most quickly at I = 2. This is a very rough model for vocale voicing, but voicing data are virtually non-existent for pre-Schnitger vocale archetypes or their modern American practitioners. A recent YouTube video featuring George Taylor and John Boody contains an excellent discussion of vocale cutups: https://www.youtube.com/watch?v=_NT65GJNBrU.

American classically inspired voicing has evolved. In their description of their lovely Opus 24 in The Diapason, Richards, Fowkes & Co. stated that “voicing our pipes a little slower relaxes the speech and helps them blend better.”32 “Slower voicing” does not mean that a pipe’s speech is slow to form, it means quite the opposite. With slower voicing the speech is slower to overblow to the octave when blown on higher pressure, and in that condition Ising has shown that the fundamental forms more quickly. To obtain this condition we raise the cutups and/or the languids. (Harmonic flutes will more easily overblow to their octave with languids set very low.) Gottfried Silbermann built very fast speech and “slower voicing” into his pipes with his extended upper lip, extremely high languids, and generous cutups. The blend of a Silbermann chorus is exceptional.

Bruce Shull has worked with John Brombaugh, Taylor & Boody, and Paul Fritts & Co. He has recently written a very informative article on the tonal qualities of sand-cast pipe metal. When voicing pipes made with this metal,

. . . [they] behave the best when they are rather open at their wind[flue]ways. . . . A counter bevel on the front edge of the languids is quite frequently found in antique pipework; today this can be achieved simply by abrading the front edge of the languid with a simple brass file with cross hatching scribed into one surface. The inside edge of the lower lip should remain smooth and must have a burr-free inside edge. . . . It may be that voicing styles that utilize nicking of the languid front edge will produce tonal results that are not very different between sand-cast and stone-cast pipe metal. . . . The organs [voiced with these pipes] have a solid and full sound with a very sweet character at the same time. There is a hint of breath in the sound due to the open windways and abraded languid fronts but the speech is immediate and yet gentle, and the blend is superb. The speech is such that the voicers find themselves doing less “fussing” with the pipes, and, in fact, the pipes have taken much less time to finish on site.33

Although Silbermann’s resonators had thin and very stiff walls of about 90% hammered tin, he would no doubt agree with these voicing comments.

The power of inductive logic

The sound of a pipe organ can spark strong emotions, and the subject of voicing can spark fierce emotional debate. Voicing is indeed complex. We could spend a lifetime exploring its wonderful variety, but with some effort it is comprehensible.

This brings us full circle to the leading quote in this article: “Inductive logic is much more difficult­—but can produce new truths.” Inductive logic requires data, and the collection of data and its analysis requires effort. Some may find the effort required by inductive logic inconvenient if they accept the idea that all opinions have equal value, an extraordinary belief that curiously took root in American public education in the 1970s. But we have known since the time of Francis Bacon’s formalization of the scientific method that Nature yields only to data and cares nothing about our opinions. The inductive models in this article represent a significant effort to understand the data, and as new data emerges these models will no doubt be refined or replaced by others with better models. This is the power of inductive logic.

Silbermann’s inductive brilliance

The organs built at Freiberg in 1714 and much later at Großhartmannsdorf in 1741 are voiced on similar wind pressures. The regularity and similarity of the toes and flueways in these two organs establish that Silbermann devised successful models of voicing at the beginning of his career. Many organbuilders experiment with these complex variables to improve their sound over the course of their careers. Data previously published in The Diapason suggest that Silbermann’s regularity is probably unique among organbuilders. Figure 21, for example, shows that the Hooks treated toe constants as a completely free variable.34 The regularity of Silbermann’s work may imply a limited tonal palette, but his youthful brilliance in finding a set of scaling and voicing models that would work in a wide range of acoustics and wind pressures is simply astounding. 

Silbermann’s data reveal an intellect that embraced inductive models. These models are not recipes from received wisdom. They are unique to Silbermann, and they exhibit the traits of inductive logic based on experimental data. Consider for a moment that Silbermann, the son of a carpenter, was not likely given a formal education in mathematics and science; this was the province of the wealthy and political elite during the time of Silbermann’s youth. Greß’s data and their implied theoretical models of voicing clearly represent an intellectual tour de force. Silbermann’s sound is indeed controversial, but Silbermann’s insights can teach us a great deal about the theoretical foundations of tonal design and voicing.

Organ literature often waxes nostalgic about the “secrets” of the old masters. The secret to their success was just the hard work of analyzing the problems they faced. Whether we are looking at the balanced ratios of the Isnards, the carefully calculated toes and flueways of Silbermann, or the Romantic sounds of Cavaillé-Coll, we see the work of analytical minds in the pursuit of artistic beauty. It may come as a surprise to know that Cavaillé-Coll and John Brombaugh were both trained as engineers. There is no gulf between art and science; they are mutually bound.

Silbermann’s unique sound

Gottfried Silbermann’s sound does not follow classical North German or French models. A typical North German chorus has a restrained power from its more closed flueways, a chorus fire supplied by its mixtures, and a strong fundamental supplied by the very wide, leathered shallots of its chorus reeds. A Classical French chorus has a restrained power from its more closed toes and a chorus fire supplied by its reeds. Silbermann combines powerful French reed fire with a powerful flue chorus derived from deep flueways, more open toes, and the widest possible mouths. Gottfried Silbermann’s sound is not a synthesis of classical French and North German organs, it is unique, and its blend and clarity make the sound of Bach come alive. Follow this YouTube link to the carefully restored Silbermann at Lebusa: https://www.youtube.com/watch?v=oOoSkB2UVMw.35 The temperament is a form of meantone devised by F.-H. Greß.36

Meantone

Gottfried Silbermann’s voicing and blend work very well in meantone. With the exception of “big city” organs such as the Frauenkirche organ in Dresden, Silbermann maintained the use of a very mild 1⁄6-comma meantone even when confronted with strong opposition from Johann Sebastian Bach. There is no dispute that equal temperament is essential to a vast range of wonderful literature, but we have also come to understand that meantone has a tonal beauty and gravity sorely lacking in equal temperament. This was a concept well understood by Bédos, who abhorred equal temperament.37 Meantone was perhaps a part of Silbermann’s French legacy. 

Very few of Silbermann’s organs have survived in any form of meantone, but the lovely organ in the Freiberg Dom had organists who mostly succeeded in protecting it from the good intentions of its restorers. Here is a soundclip of the end of Bach’s Passacaglia and Fugue in C Minor, BWV 582, written in Bach’s early years, and played on the Freiberg Dom organ in 1980 in an approximation of its original meantone. The Picardy shift to C major at the end of the fugue resolves in a radiant third. This is Gottfried Silbermann’s sound. <soundclip 5>

Uncredited images reside in the collection of the author. Fr. Thomas Carroll, S.J., graciously suggested clarifications in the prose of this article.

Notes

21. Robert A. Heinlein, The Notebooks of Lazarus Long (New York: G. P. Putnam’s Sons, 1973). 

22. In 1972 I asked Dirk Flentrop for permission to measure his pipework and organs, which he graciously gave, adding that imitation was the finest form of flattery. Flentrop went on to predict that I would use my observations of his work to find my own sound (“Your ears will be different than mine”). He was a generous teacher, and secure in his knowledge. The Flentrop data shown in Figures 14, 16, 19, and 20 were taken in 1978 with the kind permission of David Rothe. The Hook data were taken in 2000 with the kind permission of Fr. Thomas Carroll, S.J. The Isnard data can be found in the original source in Note 26 and fully graphed in the source in Note 23.

23. Michael McNeil, The Sound of Pipe Organs, CC&A, 2014, Amazon.com. The toe constant equation: diameter of the toe = √ (toe constant*4*mouth width fraction*pipe diameter).

24. Heimo Reinitzer, Die Arp Schnitger-Orgel der Hauptkirche St. Jacobi in Hamburg, 1995. This is one of only three publications known to the author to include complete data for understanding the sound of an organ, i.e., its pipework, windchests, wind system, temperament, action, and layout. The other examples can be found in the author’s “The 1755 John Snetzler Organ, Clare College, Cambridge, restored by William Drake, Ltd., Joost de Boer, Director,” The Diapason, September 2019, pages 17–21, and “The 1864 William A. Johnson Opus 161, Piru Community United Methodist Church, Piru, California,” The Diapason, August 2018, pages 16–20, September 2018, pages 20–25, October 2018, pages 26–28, and November 2018, pages 20–24. I use Jahnn’s data for the Hauptwerk 16′ Principal on page 117 for Schnitger’s voicing; located in the façade, these pipes may have been the least accessible to changes in voicing. The restorer, Jürgen Ahrend, states on page 252 that the cutup, flueway, and toe hole data in this book were taken after his voicing (“. . . nach meiner Intonation”). Ahrend had to deal with previous interventions, and the current sound reflects his voicing. The toe data of the 16′ Principal taken after the restoration show extremely wide variations and some excessively open toes; Jahnn brilliantly solved this problem in 1925 by measuring the smallest diameters in the wind conduction between the windchests and the offset pipe feet—these are the values shown in Figure 14.

25. The Sound of Pipe Organs, pages 64–80. 

26. Pierre Chéron and Yves Cabourdin, L’Orgue de Jean-Esprit et Joseph Isnard dans la Basilique de la Madeleine à Saint-Maximin, ARCAM, Nice, 1991. The Isnard Grand Orgue toe/flueway area ratios on page 166 are almost exactly 1 up to 1′ in pitch for the entire principal chorus including both mixtures. The 8′ Montre deviates because it was revoiced in 1885. See page 59 on “closed up flueways” and page 175 on languids, which have about 50-to-58-degree bevels and about 75-degree counterbevels that slope inwards (counterbevels are more commonly vertical). Per my on-site observations on June 24, 1995, the upper lips are aligned with the lower lips, and the languids are lower than Silbermann’s, where the top of the Isnard counterbevel is level with the top edge of the lower lip.

27. McNeil. The Sound of Pipe Organs, pages 177–182.

28. Pierre Chéron and Yves Cabourdin, L’Orgue de Jean-Esprit et Joseph Isnard dans la Basilique de la Madeleine à Saint-Maximin, pages 132–133.

29. McNeil, The Sound of Pipe Organs, page 94.

30. Richards, Fowkes, & Co. See richardsfowkes.com/5_technical/beckerath for the Schnitger data taken by Beckerath. 

31. Vocale voicing has affinities to smooth Romantic English voicing with its very high cutups. None of the English Romantic chorus stops are harmonically rich, but they are intense with deep flueways; brightness is built by adding the smoothly voiced sounds of higher pitched stops. Instrumental voicing features harmonic richness in the individual stops, and those harmonics, when carefully voiced, can create a chorus of rich harmonics; this is the sound of a D. A. Flentrop. This distinction is also applicable to a reed chorus. The broad, leathered shallots of English and German reeds add smooth fundamental power. The rich harmonics of Clicqout, Callinet, and Cavaillé-Coll chorus reeds create a scintillating chorus depth. Much voicing resides in the broad range between these styles.

32. Opus 24, “Cover Feature,” The Diapason, May 2021, pages 26–28.

33. Bruce Shull, “Casting Pipe Metal on Sand,” Vox Humana, April 25, 2021.

34. See the toes, flueways, and ratios for E. & G. G. Hook, J.-E. & J. Isnard, W. A. Johnson, and J. Snetzler in “1863 E. & G. G. Hook Opus 322, Church of the Immaculate Conception, Boston, Massachusetts,” Part 2, The Diapason, August 2017, pages 18–21, “The 1864 William A. Johnson Opus 161, Piru Community United Methodist Church, Piru, California,” Part 4, The Diapason, November 2018, pages 20–24, and “The 1755 John Snetzler Organ, Clare College, Cambridge, restored by William Drake, Ltd., Joost de Boer, Director,” The Diapason, September 2019, pages 17–21. With the sole exception of Gottfried Silbermann, these are free variables for all other builders known to the author.

35. J. S. Bach, Komm, Heiliger Geist, Herre Gott, BWV 651, Christopher Lichtenstein, organist.

36. Frank-Harald Greß, Die Orgeln Gottfried Silbermanns (Dresden: Sandstein Verlag, 2007), pages 72–73.

37. Michael McNeil, “The elusive and sonorous meantone of Dom Bédos,” The Diapason, September 2020, pages 14–17.

Soundclips

4. [00:33] Louis Marchand, Tibi omnes angeli, Jean-Esprit Isnard, Couvent Royal de Saint-Maximin, 1774, Bernard Coudurier, BNL 112851 A, © SCAM/BNL 1995.

5. [00:55] Johann Sebastian Bach, Passacaglia and Fugue in C Minor, BWV 582, Gottfried Silbermann, Freiberg Dom, 1714, Karl Richter, Archiv 2533 441, © Siegfried Schmalzriedt, 1980.

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