pipe organ pitch

[Greg Graham]

Don, 

Jonathan's answer struck me as too much.  I've checked
pipe organs on 90 degree days and they were 30 cents
sharp, not the 120 cents his formula would suggest.  I
don't tune organs, but I measure their "A" pitch when
someone at the church asks me to tune the piano to
match the organ.  (No, I don't tune the piano 30 cents
sharp on 90 degree days).

Another complication:  flue pipes change more with
temperature than reed pipes with short resonators. 
Humidity impacts wood pipes, which increase in size
with moisture, but not metal.  The various ranks do
not move together.  

"The Art of Organ Building" by G.A.Audsley, 1905,
shows a table on page 637, "Vibration-numbers
According to Diapason Normal at Different
Temperatures".

59 degrees F, A4=435.0  
60 degrees F, A4=435.4
... etc, etc
67 degrees F, A4=438.5
68 degrees F, A4=439.0

I extrapolate this to A4=440 at 70 degrees F.

"Diapason Normal" is the French law of 1859 specifying
870 vibrations (really half a Hz cycle)per second at
15 degrees C, or A4=435 at 59 degrees F.  This chart
was intended to show where to tune at temperatures
higher than "standard".  The coefficient used is
interesting:  1/1000th of the frequency per degree. 
435 Hz goes up to 435.435 at 60 degrees.  Multiply the
frequency by 1.001 for each degree. 

At A4, you're looking at about 0.4 Hz per degree, or
about 1.6 cents/degree, theoretically, for open, metal
flue pipes like a diapason.  Other stops will vary.

Greg Graham
Brodheadsville, PA

>pipe organ pitch 
>jonathan stuchell jstuchell@verizon.net 
>Sat, 03 Dec 2005 17:40:50 -0500 

>hello,

>6 cents per 1 degree F change ( expressly for a pipe
organ)
>----- Original Message ----- 
>From: "Don Price" <dcp3@twol.com>
>To: <pianotech@ptg.org>
>Sent: Saturday, December 03, 2005 5:17 PM
>Subject: pipe organ pitch


> List -
> Can any of you knowledgeable people tell me the
approximate amount of 
> pitch change in cents per degree of temperature
change for a pipe organ?
> 
> Thanks.
> 
> Don




		
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