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Re: [Phys-L] Saving Money on Tuning a Pipe Organ

I have tangential experience tuning organs -- my father is an organist and
I sometimes had the job as a kid of holding the keys while he re-tuned the
pipes. And I have a passing interest in the physics of music.

A few initial comments.
As a baseline, a half-step is about a 6% change in frequency. (about 26 Hz
for 440 Hz "A4")
Notes played alternately that differ by 1/10 of a half-step = 0.6% (or "10
cents" in music lingo) are distinguishable by most people. (2.6 Hz for A4)
Notes played in unison are distinguishable within much less than 1 Hz using
Absolute tuning is less important than relative tuning. Hardly anyone will
notice if all the notes are a half-step high or low, as long as they are
all off similar amounts and in tune with each other. One exception is
when the organ is played with other instruments. Then being close to the
right absolute pitch is important so that the other instruments don't need
to adjust their own tuning so much.

1) Temperature primarily affects the speed of sound in air, not the
dimensions of the pipes. Speed changes ~ 0.6 m/s/C. so a change of 5C is
about 3 m/s or nearly 1%. The air speed changes would affect absolute
pitch, but would maintain relative pitch. Changes due to pipe dimensions
would be smaller. As a side note, pipes are made of different alloys and
made of wood. So thermal expansion would be different for different pipes,
so maintaining small temperature changes would be useful for keeping wooden
pipes relatively in tune with metal pipes.

2) I see humidity as a minor player for pitch. Going from 0% to 100%
humidity is about a 1% change is speed @ room temp. This will affect
absolute pitch, but not relative pitch. And again, since some pipes are
wooden, they will expand/contract from winter to summer as humidity
changes, so wooden and metal pipes will go out of tune relative to each

3) I suspect that gluing/soldering/taping the tuning sleeves would still
create problems over time, especially summer vs winter. More subtly, there
are different ways to tune instruments. Organs usually have an "equal
temper" tuning, but purists might want a different tuning for eg baroque
music. (Not many churches would ever worry about this). In any case,
being able to fix problems probably trumps trying to 'lock' a tuning into
place in the minds of organists.

5) I also suspect that many of these changes would only be clearly noticed
by the organist (or other trained musicians). As a kid, I could clearly
hear as the piped were being tuned and knew when they were close to 'good
enough' -- ie the beats disappeared. But I didn't really hear the
difference from one Sunday to the next.

On Thu, Dec 10, 2020 at 8:22 PM Bill Norwood via Phys-l <> wrote:

Hi Phys-L,

A local church was recently celebrating having just gotten their pipe
organ tuned. I responded by declaring that they could save money if
considering the following:

1. Temperature: Presumably the organ pipes are kept within a 40-degree
temperature range throughout the year, in which case there would be no
significant change in any pipe dimension, so, temperature variability would
not be an incentive for “tuning.”

2. Humidity: If humidity cannot be kept constant (within 1 or 2 %) then
the organ will never be in tune, because the humidity normally changes at
least daily irrespective of time of year. However, the average humidity is
lower in winter, but we cannot predict how cold a winter is coming.
Therefore I claim that humidity cannot be a reason for organ “tuning.”

3. Vibration: The more the organ is played the more the pipes assembly
will be vibrated, and the more the pipe sleeves will drift downward.
Therefore, after a newly-installed organ has been played for a year, and
the pipes and their mountings have gravitationally settled, then the
sleeves could be stabilized so they can no longer move.

4. No further tunings should be necessary, barring an earthquake or nearby
excavation, or other incident such as a prank, a stolen pipe, or a rat
dragging foreign matter into a pipe, or a local soprano out of control.

5. The congregation should not have been told that the organ had been
tuned, rather they should have been asked to report any changes in organ
sound as the months went by. That would have enabled objectivity. A log of
these reports would sometimes enable correlating organ sound changes with
common organ sound-affecting incidents.



Bill Norwood
U of MD at College Park
Since 1966

I have no experience tuning organs - just guitars.

Sent from my iPhone
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