humidity and unisons

[Fred Sturm]

List,
	A couple days ago, a tuning I did helped confirm some of my thoughts
about unisons going out of tune in response to humidity change. The
piano was a Wurlitzer grand out of the 50's (the time when Wurlitzer was
a hotbed of experimentation), and has tuning pins "wedged" to the plate.
(No pinblock. Web is extra thick, and drilled close to tuning pin
diameter. Tuning pins are slit up from the bottom, and wedges driven in
the slit to create a friction fit between pin and plate). 
	Obviously there could be no affect from expansion/contraction of
pinblock, since there isn't any pinblock. Yet from C4 to C8 (I didn't
start noticing until I got to C4) the right (treble side) strings were
consistently 1 to 10 cents sharp of the left side strings, with middle
strings in between. Very consistently - in excess of 90% of unisons were
this way, mostly around the 5 cent range. I had previously tuned the
piano in February, and had measured 30% humidity. This time (July) it
was 60% humidity.
	Just one more piece of evidence to confuse and confound the mind.

Regards,
Fred S. Sturm
University of New Mexico

"A mind is not a vessel to be filled, but a fire to be kindled."