1863 E. & G. G. Hook Opus 322 Church of the Immaculate Conception Boston, Massachusetts, Part 2

August 1, 2017

Michael McNeil has designed, constructed, and researched pipe organs since 1973. He was also a research engineer in the disk drive industry with 27 patents. He has authored four hardbound books, among them The Sound of Pipe Organs, several e-publications, and many journal articles.

Editor’s note: Part I of this article was published in the July issue of The Diapason, pages 17–19.


Mouth heights 

Mouth height, or “cutup,” as it is more commonly called by voicers, is the primary means of adjusting the timbre of a pipe. Low cutups will create a brighter tone with many harmonics, while high cutups will produce smoother tone with fewer harmonic overtones. For interested readers, see The Sound of Pipe Organs, pp. 68–80. In older organs, it is not uncommon to find flute pipe mouths cut twelve half tones higher than principal chorus pipes.

In the Normal Scale of mouth heights, a higher cutup value on the vertical scale will result in smoother tone. Cutups may be adjusted higher for one or both of two reasons: 1) the voicer wants a smoother timbre, or 2) the voicer wants more power at the same timbre. More power means more wind, and this means a larger toe and/or flueway to admit more wind at the mouth. More wind at the mouth will always produce a brighter tone, so the voicer can make a pipe louder and preserve its original timbre by opening the toe and raising the cutup until the timbre is restored.

Now we can understand the graphs. In Figure 6 we see that the Hook principal chorus has high cutups and that they do not significantly vary from bass to treble. Hook pushes pipes to higher power with much more open toes (Figure 8), and the voicer raises the cutups to avoid a strident timbre at the increased power. The timbres are relatively constant from bass to treble. Note the lower mouth heights of the William A. Johnson Cymbal VII, which makes its timbre brighter than the Hook voicing (also note that the Cymbal’s toes are winded as robustly as the Hook pipes in Figure 8).

In contrast, the Isnard chorus in Figure 7 shows much lower cutups in the bass and mid-range, and much higher cutups in the highest treble. We will see in the data for toe diameters in Figure 9 that Isnard is restraining his pipes for less power and voicing for an ascending treble.


Pipe toe “C” values

Pipe toe diameters can be normalized to the diameter of the pipe, the width of the mouth, and a normalized depth of the flueway. For interested readers, the derivation of this normalization is explained in detail in The Sound of Pipe Organs, pp. 43–47. Higher “C” values mean the toe is larger and flows more wind relative to its mouth width and flueway depth. This is a primary voicing tool for regulating power.

The contrast in the toe diameters of these two organs is striking in many ways. The Hook toes in Figure 8 are much wider overall than the Isnard toes in Figure 9, demonstrating the primary source of the power of the Hook. This power would normally encourage chiff in the pipe speech, but this is suppressed in the Hook by the use of very deep and regular nicking of the languids of the pipes. Ninety percent of the Isnard pipes are free of nicks, and when nicks are found, there are typically only two or three very fine, shallow nicks on a languid. Contrast this with the treatment of the 16 Open Diapason of the Hook: 22 fine nicks at C1, 20 nicks at c13, 29 nicks at c25, 24 medium nicks at c37, and 19 medium nicks at c49, all of the pipes having their nicks cut very deeply into the languid. There is no discernible “chiff” to the speech, but this is desirable for the interpretation of Romantic music. Interested readers can refer to The Sound of Pipe Organs, pp. 94–96, for a graphic illustration of the effects of such nicking on speech transients.

Figure 8 demonstrates another key element of the Romantic tradition—large toes supplying more wind and power to the bass and mid-range. In contrast, the toe constants of the Isnard are much smaller, more constant across the compass, more constant for all stops of the chorus, and exhibit a subtle rise to support an ascending treble. 


Flueway depths 

Like the pipe toe, the flueway depth also controls the flow of wind and strongly correlates to the power of the pipe. Interested readers can refer to The Sound of Pipe Organs, pp. 50–63 and 77–82. 

In Figure 10 we see another essential characteristic of Romantic voicing—a very deep flueway. Much of the Romantic voicing tradition grew out of the French Classical voicing style, which maintained deep flueways and controlled the power of a pipe by restricting its toe, much as we see in Figure 9. The restorer of the Isnard organ, Yves Cabourdin, noted that the flueways of the Isnard organ seen in Figure 11 are “closed up” relative to normal French Classic practice, yet the flueways of the Isnard are very deep relative to the common North German practice of regulating power by closing down the flueways while maintaining open toes. For interested readers, some examples of historical practice in flueway depths may be found in The Sound of Pipe Organs, pp. 50–51.

The extremely deep flueways of the Hook organ are consistent with Romantic voicing in general, along with more generous toe diameters and the nicking required to suppress chiffing in the pipe speech at the greatly increased power levels of this style. 

The flueways of the Hook organ appeared in general to be very well preserved and were very consistent. The anomalous lower value of the flueway in Figure 10 for the Hook 16 Open Diapason at c25 (4 pitch) may have been the result of handling damage to that pipe or modifications when the pitch was changed. The robust flueway depth of the Hook 16 low C pipe is literally off the chart at 4.8 mm.


Ratios of toe and flueway areas

The flow of wind and power balances are controlled by the voicer at the toe and flueway of a pipe. The ratio of the area of the toe to the area of the flueway is important. If the area of the toe is less than the area of the flueway, which is a ratio less than 1:1, it will cause a significant drop in the pressure at the mouth, and what is more important, the speech will be noticeably slower. When the area of the toe and flueway are equal, the ratio is exactly 1:1, and this is the lower limit for pipes with faster speech. Interested readers can refer to The Sound of Pipe Organs, pp. 56–63 and 114–116 for a discussion of this very important musical characteristic and its effect on the cohesion of a chorus. (A well-knit chorus may contain slower pipes or faster pipes, but never both.)

The Hook ratios in Figure 12 never descend below a ratio of 1:1 and typically ascend to extremely high values in the treble. It is this technique with which Hook obtains an ascending treble.

The Isnard ratios in Figure 13 reside at a value of 1:1 for the bass and mid-range and ascend to much higher values at the highest pitches. Like the Hooks, the Isnards achieved an ascending treble with this technique, but unlike the Hooks, the Isnards crafted the bass and mid-range ratios to values of almost exactly 1:1. The Isnard pipe speech has a lovely “bloom,” which is a direct result of these very carefully crafted ratios; the term “bloom” refers to a slower buildup of power in the initial speech of a pipe. The Hook organ also exhibits a distinct bloom, but this bloom has no speech transients, and it derives from the low resonant frequency of the wind system when it is working hard to supply wind.


The wind system 

The design of the wind system plays a large role in the dynamics of the wind and the musicality of the organ. Dry acoustics favor faster wind systems, which support faster tempos; live acoustics fill dramatic pauses with a halo of reverberation and encourage slower tempos. Wind systems can be designed to enhance the grand cadences of historic literature written for live acoustics, and such wind systems will have a slower response. For interested readers, this response can be described as the resonant frequency of the wind system, and it is fully described in The Sound of Pipe Organs, pp. 99–113, using the Isnard organ as a worked example.

Documentation of the wind system is probably the most overlooked feature in descriptions of pipe organs. The Hook’s wind system was measured in some detail, but not completely due to the constraints of time.

The wind of the Hook organ has no perceptible shake. The tutti does not noticeably sag in pitch. The speech onset of the full Hook plenum is characterized by a dramatic surge, the result of weighted bellows and large system capacitances. The current wind system shows some modification of the 1863 design, largely as a result of the 1902 addition of the Solo Division. 

The static wind pressure of the Great was measured to be 75 mm water column at c(25) of the 4 Clarion, the last stop on the back of the chest. The static wind pressure at a′′′(58) of the 16 Open Diapason was measured to be 76 mm; drawing all of the stops reduced that pressure to 67 mm.

All divisions in the organ are fed with ducts that have cross sections many times what is necessary to wind the tutti. These ducts are also very long, with the result that they are calculated to have Helmholtz resonances in the very low range of about 4 Hz; this frequency is not audible when the organ is played, suggesting that the damping of the wind system is considerable (some concussion bellows are present). The main ducts have about 0.56 m3 of volume.

The two bellows that together feed the Great and Choir (and originally also the Swell), are massive with 8.4 m3 of volume, having two inward folds and one outward fold. The resonant frequency of the two bellows, two pallet boxes of the Great division, and wind ducts as a function of their mass and volume is calculated to be 1.23 Hz. Such a low resonant frequency is the primary source of the grand surge in the tutti of this instrument. It is a musical wind with grand drama, exhibiting none of the nervousness of organs with sprung bellows. Both the mass and volume of this wind system compare favorably with the Isnard organ. And although the Hook organ features double-rise bellows and the Isnard features wedge bellows, they have very similar and low resonant frequencies at 1.23 Hz and 1.20 Hz, respectively. Figure 14 is a table showing the measurements of the wind system and its calculated resonance. 

Another important characteristic of a wind system is its wind flow and damping. The total demand on a wind system is equal to the areas of all of the toes of all of the pipes that can be played at the same time on full organ. We then look to see if the key channels can flow sufficient wind to those toes, if the pallets can flow sufficient wind to the key channels, and if the wind ducts can flow sufficient wind to all of the pallets. This analysis was performed on the Isnard organ (see The Sound of Pipe Organs, pp. 120–127), with the interesting result that the Isnard wind trunk just barely flows adequate wind for the coupled principal choruses of the Grand Orgue and Positif, but it is wholly inadequate for any form of tutti. This sort of restriction is not uncommon in older organs, and it performs the function of adding significant resistance to the wind flow, which in turn dampens Helmholtz resonances in the cavities of the wind system, e.g., wind shake from the wind trunks and pallet boxes. We do not have enough data for all of the stops of the Hook to perform this analysis, but the very large cross-section of the wind trunk suggests that it has much more winding than the Isnard, and that would be consistent with a Romantic organ and the requirement that it support a full tutti. The table in Figure 15 shows the data for wind flow in the windchests of the Great division.


The Great division 

There are two windchests for the Great division, split diatonically C and C# with the bass notes at the outer ends and a walkboard in the middle. Figure 16 shows the pipes on the C side windchest from the 8 Open Diapason Forte at the left (front of the chest) to the treble end of the III Mixture at the right. The order of stops is:


8 Open Diapason Forte

8 Clarabella

16 Open Diapason

8 Viola da Gamba

8 Open Diapason Mezzo

4 Octave

4 Flute Harmonique

3 Twelfth

2 Fifteenth

III Mixture

V Mixture

VII Cymbal (Johnson, 1870)

16 Trumpet

8 Trumpet

4 Clarion


Figure 17 shows the treble end of the mixtures on the C side. The toeboard on the left contains both the III Mixture and V Mixture. From left to right, we see the III Mixture, V Mixture, and on the right toe board, the later addition of the VII Cymbal (red arrow).

Most of the treble pipes are cone tuned and exhibit almost no damage. This is a tribute to the tuning skills of the Lahaise family. Few organs of this age have survived with such intact mixture pipes. The pre-restoration photos of the Isnard organ at St. Maximin show the more typical fate of such pipes.

All of the tin-lead pipes in this organ are constructed of spotted metal, with the notable exception of the Cymbal (added by Johnson in 1870), which is planed metal. This accounts for the obvious difference in the construction of the rackboard for this stop. The VII Cymbal (red arrows) includes a third-sounding rank, and in the style of Johnson it is silvery (lower cutups) and restrained in power (very narrow pipe diameters and mouth scales). Although no records exist, there must have been a fascinating story behind the inclusion of a competitor’s mixture in this organ.

Figure 18 shows the back of the C side Great chest. The order of reed stops, from left to right, is: 16 Trumpet, 8 Trumpet, and 4 Clarion. Note that the 4 Clarion is cut dead length in all pipes except the newer, slotted low C pipe added at the time of repitching the organ. Trebles of the 16 and 8 ranks are also cut dead length without slots. The intent here is obvious: don’t tune these reeds on the scrolls, tune them on the wire.


General observations


16 Open Diapason

All of the pipes of the 16 Open Diapason from the mid-range downward into the deep bass exhibit very bright harmonic content. The reason for this becomes apparent with a close examination of the middle D pipe. When the organ was repitched from A=450 to A=435 Hz, a new low C pipe was made for many of the stops and the original pipes were moved up one half step. The tuning distance between 435 Hz and 450 Hz is less than a half step, with the result that the pipes were now much too flat. The scrolls were then rolled down to bring the pipes into tune at 435 Hz. We can see from Figure 19 that to achieve correct tuning on the middle D pipe, the tin-lead scroll was completely removed and the zinc resonator was crudely cut and broken to make the slot deeper.

This was apparently not sufficient to bring this pipe into tune. Figure 20 shows that the toe of this pipe was crudely opened and flared outward without the benefit of a normal toe reamer or toe chamfering tool. This is very informative because it explains the much brighter timbre of this pipe relative to its treble or other foundations. The opening of the toe increased the pitch and brought the pipe into tune, but at the expense of more power and a much brighter timbre relative to the original voicing. Even with this increased power it would have been possible to have preserved the original timbre by slightly raising the cutup. Inspection of the upper lips indicates that this was not done; the upper lips of all pipes are slightly skived to about one half of the metal thickness, and this was still intact on all pipes. Note that the crudely damaged toe shows bright metal; there was no bright metal on the upper lips, indicating original cutups but modified toes. This voicing damage is typical throughout the bass of this stop. 

Figure 21 shows the back of the low D façade pipe. Note that the tin-lead scroll is completely missing, the zinc is rolled back at the bottom of the slot, and the tin-lead adjacent to the top of the slot is bent outwards on both sides. The author verified that the wind to the toe was likely altered as well; the wooden slides in the toeboard that regulate wind flow were completely open. The façade pipes were all speaking on maximum wind. Figure 22 illustrates the condition of the scrolls in the back of the façade for 16 c, 16 G#, 8 C, 8 D, 8 E, and 8 F#, going from left to right in the figure.


8 Open Diapason Forte

The cutups appear original, the toes were crudely opened, and this stop indeed sounds too loud and too bright relative to any other 8 stop. In fact, this stop obliterates the sense of chorus when using it in the traditional French fonds. One would normally expect the 8 Forte to be slightly more powerful, but less bright, than the 8 Open Diapason Mezzo; they would then combine as a fine chorus. In fact, this stop is much more powerful than the Open Diapason Mezzo and also brighter. This rank shows the same tuning modification seen in Figure 19, and the toes of this rank were opened in the same crude manner seen in Figure 20

While there is some evidence of selective toe adjustment in other stops, no other ranks show such crude treatment and excessive opening of the toes. They have normal chamfers and round bores. Lending further evidence to the hypothesis that this was damage inflicted at the time of repitching the organ, it was seen that the same crude method of opening the toes was applied to all of the new low C pipes in all of the ranks.

We are fortunate in at least one respect. The workmanship during the repitching was very crude, and this allows us to better understand the order of events and the anomalous tonal balances.


III Mixture

The mixture pipes were all moved up one half step when the organ was repitched, widening the scales by a half step and moving the breaks up by the same amount. The new pipes added at low C were crudely matched in diameters, mouth widths, and toes. The width scales of the fifths are about two half tones narrower than the 4Octave, similar to the scaling of the Twelfth. The octaves are as wide as the foundations. The current breaks are:


C1 2 113 1

c#26 4 223 2


V Mixture

Although not measured, the flueways were visually consistent with other Hook stops. This mixture is scaled about 3 to 5 half tones narrower than the foundations. The current breaks are:


C1 2 113 1 23 12

c#14 223 2 113 1 23

c#26 4 223 2 113 1

c#38 8 4 223 2 113

c#50 8 513 4 223 2


VII Cymbal (Johnson, 1870)4

Although not measured, the flueways were visually consistent with the other Hook pipework. This mixture, designed and built by William A. Johnson and installed in 1870, is 6 to 7 half tones narrower than the foundations. It has similar robust winding in its toes and flueways to the Hook work, but it is cut up relatively lower than the Hook mixtures, giving the Johnson mixture a more silvery timbre. It is a magnificent sound and provides a scintillating crown to the principal chorus of the Hook. Unlike the spotted metal of the Hook pipework, these Johnson pipes are all made of planed metal, probably containing Johnson’s typical alloy of 33% tin.5 This stop includes a third-sounding rank; its current breaks are:

C1 135 113 1 23 12 13 14

c#14 2 135 113 1 23 12 13

g20 223 2 135 113 1 23 12

c#26 4 223 2 135 113 1 23

g32 513 4 223 2 135 113 1

d#40 8 513 4 223 2 135 113

c#50 16 8 513 4 315 223 2 ν

Notes and Credits

All photographs, tables, graphs, and data are by the author except as noted.

4. Huntington, Scot L., Barbara Owen, Stephen L. Pinel, Martin R. Walsh, Johnson Organs 1844–1898, OHS Press, Richmond, Virginia, pp. 17–18.

5. Elsworth, John Van Varick. The Johnson Organs, The Boston Organ Club Chapter of the Organ Historical Society, Harrisville, New Hampshire, 1984, p. 45.

To be continued.

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