[CAUT] temperature and pitch

[Ron Nossaman]

Jeff Tanner wrote:

> Ron,
> I'm curious what happens to the tuning after you close them back up? 

Yea, me too. I assume they warm up some and go flat. I do know 
that when I unwrap them for tuning, after I give the strings a 
bit of time to equilibrate in temperature, they are very 
close, and that's six months and a major seasonal change since 
the last tuning. If they do this six months after the tuning, 
I have to presume they do the same thing every time they are 
uncovered for playing for classes, services, or whatever. As I 
said, it was pretty alarming the first time I pulled the cover 
off after the D/C installation, but I haven't found any ill 
effects from it. I notice that with the summer tunings, the 
air coming out of the piano is warm, but doesn't feel overly 
moist, while the winter tunings produce obvious moisture too. 
Since the pitch is pretty much on in both seasons, the D/C is 
obviously doing it's job, and I suspect the winter (piano) air 
feels moister compared to the 25%RH air I'm breathing than 
compared to the 65%RH summer air.


>I 
> have a situation in a small college teaching studio where the AC is 
> uncontrolled. It will usually be 63 degrees in August and somewhere 
> around 80% RH. Pitch swings were wild, so I installed a dehumidifier 
> only system.  I'm thinking of carrying a space heater with me next time 
> to warm the room some before I open up the 2 Yamaha P22s. I figure if I 
> let the strings cool down to the room temp, then tune them, then close 
> the piano back up, the tuning will go haywire in 20 minutes.

It probably will, but if the RH% inside the piano is kept 
pretty close, and you open the piano to a temperature similar 
to that at which you tuned it, I think there's a pretty good 
chance the tuning will be better than you expect. The humidity 
control is by far the more important thing. I noticed years 
ago that the funky old nasty spinets in dinky little country 
churches kept at 55° all winter stayed in tune at six month 
intervals far better than the big city churches that heated to 
73° all winter.
Ron N