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

[Paul Nord <Paul.Nord@valpo.edu>]

Bill,

I suspect that everything you said is correct to first order.  See also
Randall Munroe's withering critique of physicists:
https://imgs.xkcd.com/comics/physicists.png

We have a set of four organ pipes as part of our demonstration equipment.
The ratio of their lengths are 1, 4/5, 2/3, and 1/2.  A clever alum (now on
the faculty at Baylor) asked a great question.  If the length is the reason
for the pitch, why are the cross sections all different?  The apparatus is
designed to show a simple relationship but utterly fails to hide the true
complexity of the construction of a real instrument.  I suspect that the
primary reason for the cross section adjustment is the voicing of the
pipe.  That is, principally, making the pipes sound similar by adjusting
their overtones in similar ratios.

Short answer: What they like to refer to as simply "tuning" may be fixing a
couple of odd pipes that have developed problems.  A tuning sleeve may have
slipped.  A leather seal may have cracked.  A little too much dirt may have
gotten into the valve mechanism.

Paul




On Thu, Dec 10, 2020 at 8:22 PM Bill Norwood via Phys-l <
phys-l@mail.phys-l.org> 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.
>
> DID I GET THIS RIGHT?
>
> Thanks!
>
> Bill Norwood
> U of MD at College Park
> Since 1966
>
> P.S.
> I have no experience tuning organs - just guitars.
>
> Sent from my iPhone
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