Charles Lightfoote asked [040716 MMDigest, Compensating Organ Pipe
Tuning for Air Density]:


>> Can anyone help me find some graphic or tabular representation of
>> the effect of heat and humidity on pitch as it relates to pipe organ
>> tuning?


I have a chart which states pitch variations over a range of temperatures
in degrees Fahrenheit for the standard pitch of A = 440 Hz :

deg F.  Hz

 40  431.3
 45  433.4
 50  435.5
 55  437.6
 60  440.0
 65  441.8
 70  444.0
 75  445.6
 80  448.2

This, of course, only applies to flue pipes, as Robbie points out, but
reeds change pitch only very little.  I don't know of any appreciable
changes caused by humidity variations except that bellows-operated
organs always tend to run out of wind more easily in dry weather, and
when the pressure drops the effect is more noticeable on the reeds,
throwing them wildly out-of-tune with the flues.

Regards,
John Page, UK