[pianotech] Fork and piano temp. and pitch

[Mark Schecter]

Hi, all.

The discussion about tuning a new fork got me thinking, and I'd like to 
get reactions to the proposition below.

Given that 440 is the target, and setting aside exceptions like visiting 
artists, because the same principles apply: As we know, the pitch of a 
piano whose temperature changes will also change. When it gets colder, 
due to plate and string contraction, the pitch rises, and vice versa. 
(Granted, humidity also has its effects, but they are slower-acting, and 
deserve separate consideration).

So, if we find a way to ensure that our fork (or other pitch source) is 
at exactly 440.0, and we tune a piano that is cold to exactly 440.0, we 
know that when the temperature in the room rises, as it inevitably will 
sooner or later, the piano's pitch will fall _below_ 440. And 
conversely, if we tune to 440.0 when the room/piano is hot, and the 
room/piano cools, the piano will then be above 440. So, despite our best 
efforts to align the world to 440, we can't control the environment, and 
the piano's pitch _will_ move opposite the temperature, and will only be 
AT 440.0 when the temperature of the piano is equal to what it was when 
last tuned.

So, here's my proposition: It would be better to tune the fork to 
A=440.0 at a nominal room temperature of, say, 70 degrees Farenheit, and 
deliberately let the fork's temperature adjust to the plate of each 
individual piano before tuning.

This way, if we tune a, say, cool piano to a slightly higher pitch 
(because the fork was slightly sharp), we know that when the room and 
piano warm up, the piano will be closer to 440 than it was when cool. If 
it actually goes below 440, due to a big temperature rise, it will end 
up _less_ flat than it would have, had it started right at 440.0. The 
converse of all this applies to a warm fork/piano as well.

So in effect, we're floating the pitch of the fork in accordance with 
the temperature of the piano, in the knowledge that temperature change 
will affect both similarly.

This also has interesting implications for ETD users' choices about 
where to set pitch, as well.

So what do you think?

~Mark Schecter