[CAUT] temperature and pitch

[Fred Sturm]

On Dec 17, 2009, at 2:22 PM, Jeff Tanner wrote:

> Temp under the lid - in the dark - was 73.5 and the temp on the  
> table next to the piano was 73.0, bright lights in the room, etc.   
> That's half a degree.


	I don't think a difference in temperature that small is significant.  
If it gets above 2 degrees, then maybe you start to take notice, and  
at some point it actually affects things. In my own experience of  
sticking my thermo-hygrometer various places in and on D/C installed  
pianos over 20 years or so, I haven't seen any temperature difference  
more than a degree. This includes up on top of beams in bottom cover  
installations, under a closed lid of a grand, inside a bottom panel of  
a upright, etc. That's not to say it couldn't happen, but it hasn't  
happened on any of the pianos I service.
	I suspect that bigger temperature effects (D/C produced effects, that  
is) would happen in higher humidity climates, since the drying rods  
would be activated more (though I haven't seen it here during our high  
humidity season). And that heat could build up when a piano is  
covered, especially an upright. I don't have any uprights with covers  
and with D/Cs.
	I'd be curious to know what anyone has actually measured in terms of  
temperature differences inside and outside a covered piano. I think it  
would be especially interesting to know about grands with full length  
covers, since they are likely to be concert instruments. If there is  
enough temperature build up to cause pitch drift for 15-20 minutes  
after uncovering, that would certainly kill the deal for me. I can't  
spend that long twiddling my thumbs. A lot of times there is just a  
half hour window of access to the hall for a touch up, and losing half  
of it waiting for the instrument to settle down is out of the  
question. And I can't see having the performer uncover an instrument  
and experience pitch and tuning drift for that long, and it not being  
a pretty significant problem. Even 5 to 10 minutes would be an issue,  
though maybe more livable.
	I think a few on the list have installed such covers on pianos with  
full D/C systems, so maybe they have some experiences to share that  
would shed some light. Seems like an important thing for us all to know.
Regards,
Fred Sturm
University of New Mexico
fssturm at unm.edu