temp change=how much pitch change?

[David Ilvedson]

I'm tuning 1 or 2 Yamahas before each performance here in San Francisco.   CFIII and C7...the last 2 performances I found the AC was blowing cool air into the orchestra pit...the piano was +2 cents or there abouts.   I didn't really notice the AC until I had committed to bringing the piano down to 440.   I was under the impression the AC would be turned off...HA...and fully expected the piano to to be flat the next day...but it was right at pitch AND the AC was on again.   Amazingly they have it being dumped into the pit.   The orchestra routinely covers the vents so they don't get too cool.    Anyway, this morning no AC and the piano was right at pitch...2 shows today...this evening (after a great day at the California State PTG Convention) I tuned again...AC blowing under the piano...;-[...right at pitch or very close...them is stable pianos those Yamahas...

David Ilvedson, RPT
Pacifica, CA  94044

----- Original message ----------------------------------------
From: "John M. Formsma" <john at formsmapiano.com>
To: "Pianotech List" <pianotech at ptg.org>
Received: 2/10/2007 7:26:25 PM
Subject: temp change=how much pitch change?


>Regarding primarily large concert pianos, does anyone have data on how 
>much the pitch changes with temperature fluctuations?

>This is a question I'll no doubt answer in time as I get more experience 
>servicing concert grands. But I regularly service only one Steinway D, 
>and I haven't worked with it long enough to know how it reacts to 
>temperature changes. It has a DC system, though, which keeps it very 
>close - as long as it's plugged in and in its storage area.

>Scenario:
>Yesterday, piano was -2¢, so it was tuned to A440 in one pass since I 
>was coming back today to check it again. Temp was 67.6°F, and RH was 26%.

>Today, piano was about 3-4¢ flat (a little more in low tenor). Temp was 
>72.9°, with the humidity at 25%. So I'm seeing the most likely cause of 
>the change in pitch is the thermostat (and body heat from the orchestra 
>as well). OK, I think I understand all the whys behind the changes, but 
>I had no idea that 5° would make that much difference. After talking 
>with a piano tech friend of mine who routinely takes care of several 
>D's, he confirmed that these pianos are indeed that sensitive to the 
>temp change.

>For future reference, does anyone have data on how much change happens 
>with temperature fluctuations like this? I could say, based on my first 
>non-scientific collection of observation data, that it changes about 
>3-4¢ for every 5° of temperature increase. <g>  Is that about right 
>generally?

>What do you guys do? Do you not worry about where the temperature is? If 
>you think it will be different at performance time, do you set the pitch 
>accordingly, and hope it changes in your favor? Or do you simply tune it 
>to A440 and don't worry about it?

>Another thing that's frustrating is that I tuned it yesterday with the 
>stage lights on, so as to minimize the pitch change that comes from 
>lights. But today, it was back in the little storage room and the stage 
>is set up for the orchestra. Apparently, the piano is coming out after 
>intermission. ?? I didn't look at a program, so I dunno. But anyway, it 
>kind of stinks because today the unisons were all wobbly anyway - no 
>telling what happened when the lights hit it tonight. Oh well, at least 
>I have one thing in my favor: most people aren't as sensitive to pitch 
>as tuners are, so I'm sure I'm overreacting to what was probably a very 
>minor issue, if noticed at all. <g>

>Thanks for any help with this.

>JF