temp change=how much pitch change?

[Andrew and Rebeca Anderson]

My late mentor did some measuring.  S&S D tuned 
to 441hz at A4 under a single light was just 
under 440 hz under full stage lighting.  I'd have 
to dig in the archives but he had a Fahrenheit to 
cents ratio with in normal tuning tensions.

Probably why Steinway literature recommends tuning the D to 441.

Andrew Anderson

At 09:26 PM 2/10/2007, you wrote:
>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