Charles D. Lightfoote wrote, "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?"

If memory serves, the usual compensation is 6 cents per 1 degree
Fahrenheit of change.  Applied to the fairground organ (raised by
Robbie): If you tune in the morning at 62 degrees F., and expected 79
degrees F. at performance time, you would tune the flue pipes 1/2-step
flat.

But herein lies a complication.  Reed pipes with "full length"
resonators (i.e., middle C is about 2 feet long) will more closely
follow the same temperature and pitch change as the flue pipes.  Reed
pipes on mechanical organs are often 1/2-length or even 1/4-length.
With less resonator to influence the pitch, they tend to stay pitched
by the tuning wire.  And if you have free reeds, their pitch is even
less affected by the resonator, and therefor a change in temperature.

The best method will depend on your particular instrument and the ease
of tuning.  May I suggest that if you must perform in conditions that
make your instrument sound horribly out of tune, to either play the
reeds alone, the flues alone, or skip the performance.

Nothing ruins music like bad intonation (tuning).  Have you noticed how
many people _expect_ band organs to play out of tune?

Regards,
Robert Linnstaedt
The Organ Shoppe