The Boardwalk Hall Auditorium Organ in Atlantic City has an official total of 33,112 pipes, and four of its voices stand on 100 inches of wind, which its keepers describe as double that of any other organ ever constructed (Convention Hall Organ Society, Midmer-Losh Opus 5550 history). At the scale of a single pipe, a laboratory flue pipe needs anywhere from 26 ms to 160 ms to settle into its note, depending only on how fast the air pressure rises under its foot (Castellengo, CNRS, ISMA 2004). The classical end correction of 0.6133 times the pipe radius still matched measured pressure profiles in 2025 (Schefter et al., Acta Acustica 2025), and most organs still run on just 2 to 4 inches of water column (Toevs, The Diapason). We aggregated data from Acta Acustica, Acoustics Today, Sensors, the Organ Historical Society’s Pipe Organ Database, the University of Edinburgh, CNRS, The Diapason, Duke University Chapel and the bodies that own the largest organs. Like violin tonewood research, organ acoustics has moved from workshop lore to measured numbers, and the building matters as much as the instrument, as concert hall reverberation data show.
A quick glossary for the rest of this roundup: a flue pipe is a whistle-type organ pipe with no reed, where a flat jet of air from a narrow slit (the flue) strikes a sharp edge (the upper lip, or labium) at the pipe’s mouth. Voicing is the hand adjustment of that mouth and airflow to give each pipe its sound. Scaling is a pipe’s diameter or width relative to its length.
TL;DR
- The Boardwalk Hall organ in Atlantic City has an official total of 33,112 pipes, with four voices on 100 inches of wind (Convention Hall Organ Society, Midmer-Losh history).
- The Wanamaker Organ in Philadelphia has 28,750 pipes in 464 ranks, the most ranks of any pipe organ, and weighs 287 tons (Friends of the Wanamaker Organ).
- Töpfer’s classic scale gives an 8 ft C diapason pipe an inner diameter of 155 mm, shrinking by about 1 : 1.682 per octave (Rucz et al., Acta Acustica 2025).
- Most organs operate on a wind pressure of 2 to 4 inches of water column (Toevs, The Diapason, Organ Acoustics at High Altitudes).
- One organ pipe took 160 ms, 45 ms or 26 ms to settle for slow, short and impulsive attacks (Castellengo, CNRS, ISMA 2004).
- A mechanical-action pallet opens fully in typically around 30 ms, far faster than the best human reaction time of around 100 ms (Woolley, University of Edinburgh, The Diapason October 2013).
- The classical open-end correction of 0.6133 times the pipe radius fitted measured pressure profiles with R² ≥ 0.998 (Schefter et al., Acta Acustica 2025).
- Narrow string stops produce more than 20 harmonic partials (Miklós, Angster and Rucz, Acoustics Today 2017).
- A 32 ft pipe sounds at 16 Hz and is felt more than heard (McNeil, The Diapason, the 1750 Gabler organ at Weingarten).
- Mean indoor temperature in 18 UK churches rose 3.4°C between 1966 and 2024 (Bingley, Knight and Xing, Buildings and Cities 2025).
- A 1°C change in air temperature shifts organ pitch by approximately 1 Hz (Curteis and McVicker, Building Conservation Directory 2025).
1. Pipe Scaling: Diameter, Mouth Width and Cut-Up
Scaling is classic organ mathematics, and it is still being rewritten. Töpfer’s nineteenth-century rule shrinks a pipe’s diameter by the fourth root of 8 (about 1.682) per octave, which means the diameter does not halve at the octave as the length does. Because 1.682 is 2 raised to the power 3/4, the diameter only halves after 4/3 of an octave, that is (4/3) x 12 = 16 semitones, so treble pipes end up relatively wider for their length than bass pipes.
The cut-up is the height of the mouth opening between the lower lip and the upper lip, and it is the voicer’s main control. In a 2025 Acta Acustica study, the reference wooden pipes had a cut-up of 4/15 of the mouth width, while Joseph Gabler cut the mouths of his highest 1/8 ft mixture pipes at Weingarten to about 40% of their mouth widths. The same 2025 study showed that a rule built on equal wall losses can make a full wooden diapason rank about 15% narrower while keeping a similar timbre and attack, which matters in crowded organ cases (Rucz et al., Acta Acustica 2025).
| Metric | Value | Source |
|---|---|---|
| Töpfer reference inner diameter of an 8 ft C diapason pipe (about 65 Hz) | 155 mm | Rucz et al., Acta Acustica 2025 |
| Diameter reduction per octave under the Töpfer scale | 1 : fourth root of 8 (about 1 : 1.682) | Rucz et al., Acta Acustica 2025 |
| Cut-up (mouth height) of the traditional reference wooden pipes, as a share of mouth width | 4/15 | Rucz et al., Acta Acustica 2025 |
| Total width of an 8 ft wooden diapason rank of 37 pipes, traditional scale vs new equal-loss scale at 80% width | about 2.95 m vs about 2.51 m | Rucz et al., Acta Acustica 2025 |
| Mouth height of Gabler’s highest 1/8 ft mixture pipes, as a share of mouth width | about 40% | McNeil, The Diapason, the 1750 Gabler organ at Weingarten |
| Extra width Gabler gave his mixture pipes from 1/2 ft to 1/8 ft pitch (one halftone of scaling = 0.5 dB of power) | 8 halftones | McNeil, The Diapason |
| Mouth height and windway depth of a measured wooden Bourdon (stopped flute) pipe | 18 mm and 0.5 mm | Bordoni et al., Sensors 2024 |
Context: the 15% figure is our arithmetic, (2.95 - 2.51) / 2.95 = 0.149. The Gabler measurements come from Michael McNeil’s analysis in The Diapason, which also notes that a 1/8 ft pipe loses 5 dB of power at 500 feet in the 102-metre basilica, the reason Gabler widened his high mixtures.
2. Wind Pressure in Millimetres and Inches of Water Column
Organ builders measure wind pressure by how high it pushes a column of water in a U-shaped glass tube (a manometer): “3 inches of wind” means the air lifts water 3 inches. The Wanamaker Organ runs its divisions on 5 to 27 inches of wind, against the 2 to 4 inches on which most organs operate. High pressure buys power for huge rooms, but historic instruments show how much music was made with very little air.
Pressure matters for voicing because the jet speed grows with the square root of the pressure, approximately V ≈ 13 √P with P in centimetres of water (Steenbrugge and De Baets, Hogeschool Gent and Ghent University). Small pressure errors therefore move the jet, the attack and the pitch. In Santa Fe, at 2,127 m, a rise from 3 to 3 1/4 inches “significantly impacted tuning and sound quality” of Fisk Opus 133 (Toevs, The Diapason).
| Metric | Value | Source |
|---|---|---|
| Typical wind pressure of most organs | 2 to 4 inches of water column | Toevs, The Diapason, Organ Acoustics at High Altitudes |
| Snetzler organ, Clare College Cambridge (built 1755) | 51 mm (2 inches) | The Diapason, Snetzler restoration report (William Drake Ltd) |
| Gabler organ, Weingarten (1750), manuals and pedal | 70 mm water column | McNeil, The Diapason |
| Sydney Town Hall Grand Organ: Echo division flues and reeds vs Solo division Tubas | 58 mm vs 256 mm (2 1/4 vs 10 inches) | Organ Historical Trust of Australia |
| Wanamaker Organ, range across divisions and regulators | 5 to 27 inches | Friends of the Wanamaker Organ |
| Boardwalk Hall organ: most of the instrument vs its highest-pressure stops | 15 inches vs 100 inches | OHS Pipe Organ Database; Convention Hall Organ Society |
| Windchest pressure used to record the 2025 Acta Acustica test pipes | 700 Pa | Rucz et al., Acta Acustica 2025 |
| Air density at 2,127 m altitude (Santa Fe) compared with sea level | about 77% | Toevs, The Diapason |
Context: the Snetzler figure comes from The Diapason’s restoration report, which calls 51 mm “quite low”. The Sydney figures come from the Organ Historical Trust of Australia, which lists the pressure of every division in both millimetres and inches.
3. End Correction and the Resonator
An open pipe behaves as if it were slightly longer than it really is, because the standing wave inside spills a little way past each opening. That extra acoustic length is the end correction, and at the mouth of a flue pipe it is much larger than at the open top, so most voicing work is really end-correction work. A 2025 Acta Acustica study confirmed the classical 1948 value of 0.6133 times the pipe radius, with fits of R² ≥ 0.998 in every case (Schefter et al., Acta Acustica 2025).
The mouth correction is what separates organ families. For narrow string pipes the mouth correction is only about 5% of the pipe length, while broad flute pipes reach values about two orders of magnitude larger, which pushes their upper resonances out of line with the harmonics and gives the dull flute sound. Voicing can also be described by the jet’s Strouhal number, here the time the jet takes to cross the mouth divided by the period of the note: the standard value is 1/4, and voicing below it gives very stable overblown regimes.
| Metric | Value | Source |
|---|---|---|
| Classical low-frequency end correction of an unflanged open pipe end (Levine and Schwinger) | 0.6133 x pipe radius | Schefter et al., Acta Acustica 2025 |
| Nominal end correction measured on a 0.01 m radius pipe at 870 Hz | about 6.10 mm | Schefter et al., Acta Acustica 2025 |
| Difference between the classical and the frequency-dependent empirical end correction | under 3% in all cases | Schefter et al., Acta Acustica 2025 |
| Goodness of fit of the end correction models to measured pressure profiles | R² ≥ 0.998 in every case | Schefter et al., Acta Acustica 2025 |
| Mouth end correction divided by pipe length (Lm/L), narrow string pipes | of order 0.05 | Steenbrugge and De Baets, Ghent University |
| Lm/L of broad-scaled flute pipes compared with string pipes | about two orders of magnitude larger | Steenbrugge and De Baets, Ghent University |
| Standard jet Strouhal number (jet transit time across the mouth / period) | 1/4 | Steenbrugge and De Baets, Ghent University |
| Range of ka (pipe radius relative to wavelength) over which both end correction models matched equally well | 0.049 to 0.377 | Schefter et al., Acta Acustica 2025 |
Context: the mouth correction “cannot be exactly calculated”, and approximate formulas such as Ingerslev and Frobenius’s stop applying once tuning slots, sleeves or ears are fitted. Most recent available data for the Lm/L ranges: the undated Ghent voicing paper, which cites work through 2009.
4. Attack Transients, Onset Times and What Players Can Control
The attack transient is the short, noisy start of a note before the pipe settles into steady tone. In flue pipes it is governed by how fast the pressure rises in the pipe foot, which is set by the pallet, the valve in the windchest that admits air to all the pipes of one note. In Castellengo’s CNRS measurements, the faster 26 ms impulsive attack was not the one heard as most precise: the 45 ms short attack was, because inharmonic “mouth tones” appear at the very beginning of the impulsive attack before the pipe locks onto its note.
Whether an organist can shape that attack is a long-running argument, and the measurements lean against fine control. In University of Edinburgh tests, the pallet snaps open in typically around 30 ms once the key’s resistance (the “pluck”) gives way, well under the best human reaction time of around 100 ms, so a player is unlikely to be able to react and steer the pallet mid-stroke (Woolley, The Diapason, October 2013). Organists hear differences, but much of it comes from timing and note length rather than the transient itself.
| Metric | Value | Source |
|---|---|---|
| Total transient of a 475 Hz tin organ pipe for slow, short and impulsive pressure rises | 160 ms, 45 ms, 26 ms | Castellengo, CNRS, ISMA 2004 |
| Time to cross the 125 Pa speaking threshold for the same three attacks | 40 ms, 9 ms, 4 ms | Castellengo, CNRS, ISMA 2004 |
| Attack perceived as the more precise of the two fast ones | short (45 ms) rather than impulsive (26 ms) | Castellengo, CNRS, ISMA 2004 |
| Time for the first three partials of 131 Hz wooden pipes to reach steady level | about 0.4 to 0.5 s (50 to 65 periods) | Rucz et al., Acta Acustica 2025 |
| Pallet travel from starting to open to fully open, mechanical action | typically around 30 ms | Woolley, University of Edinburgh, The Diapason 2013 |
| Best human reaction time in sporting events, cited for comparison | around 100 ms | Woolley, The Diapason 2013 (citing athletics rulebook) |
| Timing difference between a slow and a fast key attack played an octave apart | approximately 30 ms | Woolley, The Diapason 2013 |
| Wind pressure swing in the pallet box when a note starts (Edinburgh model organ) | around 35% of the steady pressure | Woolley, The Diapason 2013 |
Context: Woolley’s listening tests were informal, and the 35% swing was measured on a model organ where effects “may be greater than normally encountered”. Most recent available data: Castellengo, ISMA 2004, and Woolley, The Diapason 2013. The Castellengo paper used a steady foot pressure of 360 Pa.
5. Harmonic Spectra by Pipe Type
A pipe’s tone colour is its pattern of partials, the individual sine-wave components that add up to the sound. Measured spectra show that each organ family has a fingerprint built into its scaling: the first weak partial (a spectral minimum) moves up the series as pipes get narrower. Narrow string stops produce very bright sounds with more than 20 harmonic partials (Miklós, Angster and Rucz, Acoustics Today 2017).
Voicers shape this spectrum with tiny movements. Displacing the upper lip sideways by fractions of a millimetre changes which harmonics are strong, and older experiments found that trading toe-hole (pipe foot opening) against flue width left the first harmonics unchanged. Even the mouth radiates unevenly: a 2024 study with a robot-mounted acoustic vector probe found lower intensity at the centre of a Bourdon pipe’s mouth than at its sides (Bordoni et al., Sensors 2024).
| Metric | Value | Source |
|---|---|---|
| First spectral minimum: Diapason (normal scale) vs Flute (wide) vs Salicional (narrow) pipe | 6th partial vs around the 3rd partial vs 8th partial | Miklós, Angster and Rucz, Acoustics Today 2017 |
| Number of harmonic partials in String stops | more than 20 | Miklós, Angster and Rucz, Acoustics Today 2017 |
| Sideways upper-lip displacement at which the 2nd harmonic is weakest (Ghent test pipe) | near 0.3 mm | Steenbrugge and De Baets, Ghent University |
| Harmonics left unchanged when toe-hole voicing is traded for flue-width voicing (Nolle 1979) | the first 3 or 4 | Steenbrugge and De Baets, Ghent University |
| Acoustic intensity at the centre of a Bourdon pipe mouth compared with its sides | about 30% lower | Bordoni et al., Sensors 2024 |
| Measured vs simulated fundamental of an 820 mm wooden Bourdon pipe | 104.9 Hz vs 102 Hz | Bordoni et al., Sensors 2024 |
| Power a 1/8 ft pipe loses over 500 feet in the Weingarten basilica | 5 dB | McNeil, The Diapason |
Context: the same Ghent paper notes that only “a few percent” of the jet’s energy is exchanged in the pipe, with most of the rest lost to wall friction and heat, which is why pipe acoustics is so sensitive to small geometric changes. Most recent available data for the spectral minima: Acoustics Today 2017.
6. Organ Size, Pipe Counts and the Lowest Notes
Pipe counts are where organ facts and organ legends collide. The Boardwalk Hall organ’s official total is 33,112 pipes, while the Organ Historical Society lists it at 33,114 pipes in 449 ranks, a reminder that even the owners of the largest instruments count slightly differently. Only about 60% of that 7-manual, 449-rank Midmer-Losh is back to functionality, and the restoration is anticipated to finish in 2030 (Convention Hall Organ Society).
The bass is where size turns into physics. A 32 ft pipe sounds at 16 Hz, and a 64 ft stop sits one octave lower, so its bottom note is about 16 / 2 = 8 Hz, deep in the infrasound range covered by wind turbine low-frequency noise studies. Atlantic City’s 64 ft Diaphone and Sydney’s full-length 64 ft Contra Trombone are the instruments documented with such a stop (OHS Pipe Organ Database; City of Sydney).
| Metric | Value | Source |
|---|---|---|
| Boardwalk Hall Auditorium Organ (Midmer-Losh, Opus 5550, 1932): official pipe total | 33,112 pipes | Convention Hall Organ Society |
| Same organ as listed in the Organ Historical Society database | 449 ranks, 33,114 pipes, 7 manuals | OHS Pipe Organ Database |
| Wanamaker Organ, Philadelphia: pipes and ranks today | 28,750 pipes, 464 ranks | Friends of the Wanamaker Organ |
| Wanamaker Organ: total weight vs console weight | 287 tons vs 2.5 tons | Friends of the Wanamaker Organ |
| St. Stephen’s Cathedral organ, Passau | 17,974 pipes, 233 registers | City of Passau tourism office |
| Sydney Town Hall Grand Organ (Hill and Son, 1886 to 1889) | 8,756 pipes, 127 speaking stops | Organ Historical Trust of Australia |
| Pitch of a 32 ft pipe | 16 Hz | McNeil, The Diapason |
| Instruments, builders and stoplists in the OHS Pipe Organ Database | 75,544 instruments, 8,488 builders, 31,009 stoplists | OHS Pipe Organ Database |
Context: the Friends of the Wanamaker Organ note that the instrument had 10,059 pipes when built for the 1904 St. Louis World’s Fair, and its largest pipe is more than 32 feet long. Passau’s organ has been under section-by-section restoration since 2023 (City of Passau).
7. Temperature, Tuning and the Changing Church Climate
Flue pipes go sharp as the air warms, because pitch follows the speed of sound in the air inside the pipe. Duke University Chapel’s organ tuner puts the rise at about 0.5 Hz for every degree Fahrenheit, so a rank tuned to 440 Hz at 68 degrees reads 441 Hz at 70 degrees (Duke University Chapel). That makes the organ a different tuning problem from the piano, where string inharmonicity and stretch dominate: the organ drifts with the room.
The room itself has changed. Tuners’ logbooks from 18 UK churches show mean indoor temperatures rising 3.4°C between 1966 and 2024, and a warmer church logged more than five times as many organ faults as a cooler one over ten years (Bingley, Knight and Xing, Buildings and Cities, December 8, 2025). The same paper cites the charity Pipe Up’s estimate that of the 30,000 to 40,000 pipe organs in Britain, up to four per week are being scrapped.
| Metric | Value | Source |
|---|---|---|
| Pitch rise for each 1°F rise in temperature | about 0.5 Hz | Duke University Chapel, organ tuning FAQ |
| Pitch change for a 1°C change in air temperature | approximately 1 Hz | Curteis and McVicker, Building Conservation Directory 2025 |
| Room temperature offset at which organs risk detuning | 5°F above or below the original tuning temperature | Bingley, Knight and Xing, Buildings and Cities 2025 |
| Rise in mean indoor temperature, 18 UK churches, 1966 to 2024 | 3.4°C | Bingley, Knight and Xing, Buildings and Cities 2025 |
| Rise in mean winter indoor temperature, urban churches, 1966 to 2024 | 5.82°C (0.97°C per decade) | Bingley, Knight and Xing, Buildings and Cities 2025 |
| Organ faults logged over the same 10 years: St Bride’s vs St James Garlickhythe | 50 vs 9 | Bingley, Knight and Xing, Buildings and Cities 2025 |
| Churches visited that had fully operable pipe organs | 10 of 22 (54.5% no longer in use) | Bingley, Knight and Xing, Buildings and Cities 2025 |
| Recorded tuning pitch and temperature of the 1755 Snetzler organ, Clare College | A = 422.5 Hz at 17.5°C | The Diapason Snetzler report |
Context: the Duke and Building Conservation Directory figures agree once converted: 0.5 Hz per °F x 1.8 °F per °C = 0.9 Hz per °C, close to the “approximately 1Hz” of Curteis and McVicker. Tuners therefore tune at the temperature of the occupied church; Duke’s tuner aims at the 11:00 a.m. to 12 noon Sunday service and spends at least a week on its roughly 6,700-pipe Aeolian organ.
Summary: Pipe Organ Flue Pipe Voicing & Scaling by the Numbers
| Metric | Value | Source |
|---|---|---|
| Boardwalk Hall organ, official pipe total | 33,112 pipes | Convention Hall Organ Society |
| Boardwalk Hall organ, highest wind pressure | 100 inches (four voices) | Convention Hall Organ Society |
| Wanamaker Organ pipes and ranks | 28,750 pipes, 464 ranks | Friends of the Wanamaker Organ |
| Sydney Town Hall Grand Organ | 8,756 pipes, full-length 64 ft Contra Trombone | Organ Historical Trust of Australia |
| Instruments in the OHS Pipe Organ Database | 75,544 | OHS Pipe Organ Database |
| Pitch of a 32 ft pipe | 16 Hz | McNeil, The Diapason |
| Töpfer reference diameter, 8 ft C diapason | 155 mm, shrinking about 1 : 1.682 per octave | Rucz et al., Acta Acustica 2025 |
| Wanamaker Organ wind pressure range | 5 to 27 inches | Friends of the Wanamaker Organ |
| Typical wind pressure of most organs | 2 to 4 inches of water column | Toevs, The Diapason |
| Snetzler organ, Clare College (1755) wind pressure | 51 mm | The Diapason Snetzler report |
| Classical open-end correction | 0.6133 x pipe radius | Schefter et al., Acta Acustica 2025 |
| Mouth end correction / length, string pipes | of order 0.05 | Steenbrugge and De Baets, Ghent University |
| Flue pipe attack: slow, short, impulsive | 160 ms, 45 ms, 26 ms | Castellengo, CNRS, ISMA 2004 |
| Mechanical-action pallet opening time | typically around 30 ms | Woolley, University of Edinburgh, The Diapason 2013 |
| First spectral minimum: Diapason, Flute, Salicional | 6th, around 3rd, 8th partial | Miklós, Angster and Rucz, Acoustics Today 2017 |
| Harmonic partials in String stops | more than 20 | Miklós, Angster and Rucz, Acoustics Today 2017 |
| Pitch rise per 1°F | about 0.5 Hz | Duke University Chapel |
| Mean indoor temperature rise, 18 UK churches, 1966 to 2024 | 3.4°C | Bingley, Knight and Xing, Buildings and Cities 2025 |
| Acoustic intensity at the centre of a Bourdon pipe mouth vs its sides | about 30% lower | Bordoni et al., Sensors 2024 |
Methodology and Sources
- Rucz, Esteve Fontestad, Angster and Miklós, Wall losses in straight ducts with non-circular cross sections: a scaling rule of identical losses for wooden flue organ pipes, Acta Acustica 9, 10 (2025)
- Schefter, Coyle, Cannaday, Griffin and Rokni, Comparing classical and empirical end correction models using spatial pressure measurements in flue pipes, Acta Acustica 9, 71 (2025)
- Bordoni, Odya, Kotus and Kostek, Sounding Mechanism of a Flue Organ Pipe: A Multi-Sensor Measurement Approach, Sensors 24(6), 1962 (2024)
- Miklós, Angster and Rucz, Acoustics of Organ Pipes and Future Trends in the Research, Acoustics Today, Spring 2017
- Castellengo, Flute-like instrument transients: an analytical study of mouth-tone production versus pressure rise time, CNRS Laboratoire d’Acoustique Musicale, ISMA 2004
- Steenbrugge and De Baets, Aerodynamics of flue organ pipe voicing, Hogeschool Gent and Ghent University (undated, cites work through 2009)
- Woolley, The Organ: A Dangerously Inexpressive Musical Instrument?, University of Edinburgh project, The Diapason, October 2013
- McNeil, The 1750 Joseph Gabler organ at Weingarten, The Diapason
- Toevs, Organ Acoustics at High Altitudes, The Diapason
- The Diapason, 1755 John Snetzler organ, Clare College, Cambridge, restored by William Drake Ltd
- Convention Hall Organ Society, the Midmer-Losh organ at Boardwalk Hall
- Organ Historical Society, Pipe Organ Database entry for the Boardwalk Hall organ and database home page counts
- Friends of the Wanamaker Organ, organ facts and stoplist
- Organ Historical Trust of Australia, Sydney Town Hall organ and City of Sydney, Grand Organ
- City of Passau tourism office, St. Stephen’s Cathedral
- Bingley, Knight and Xing, Church pipe organs: historical tuning records as indoor environmental evidence, Buildings and Cities 6(1), December 8, 2025
- Curteis and McVicker, Pipe organs and the building environment, Building Conservation Directory 2025
- Duke University Chapel, organ tuning FAQ
- Data watch: pipe counts differ between owners and databases (Boardwalk Hall 33,112 per the Convention Hall Organ Society vs 33,114 in the OHS database; Wanamaker 28,750 per the Friends of the Wanamaker Organ vs 28,762 pipes and 464 ranks in the OHS database), and other listings give different totals for Passau, so we cite each owner’s own figure. The OHS database lists the Boardwalk organ’s 100-inch wind as “5 stops”, the Convention Hall Organ Society as “four voices”. The 64 ft frequency of about 8 Hz is our arithmetic from McNeil’s 16 Hz for a 32 ft pipe, and no fetched source gave an independent figure. Temperature sensitivity is quoted as 0.5 Hz per °F (Duke) and approximately 1 Hz per °C (Building Conservation Directory), which agree within rounding (0.5 x 1.8 = 0.9 Hz per °C). The Buildings and Cities paper counts 12 Wren tuning books in its abstract but 11 plus one Hawksmoor church in its methods. Several physics sources are older than three years (Castellengo 2004, Woolley 2013, Acoustics Today 2017, Steenbrugge and De Baets c. 2009), and the attack perception findings rest on informal listening tests, not controlled trials. The McNeil and Toevs articles are undated online. The Boardwalk restoration (about 60% functional) is a moving figure.
- Last updated: November 7, 2026. We update this roundup quarterly, and the next refresh is expected when the Convention Hall Organ Society publishes its next restoration progress update for the Boardwalk Hall Midmer-Losh organ.