temp change=how much pitch change?

[Marcel Carey]

Hi John,

It's pretty unpredictable but in a way it is predictable. The thing is
that with temperature change, longer strings elongate more than short
strings. So what I find is the pitch will move more in the tenor section
than in the treble. What I like to do (which isn't always possible) is
to tune after the lights have been on for a while. If not possible, I
might leave the piano a tad sharp in the tenor and not stretch my
octaves as much as I normally would. But I will come back after dress
rehearsal and re-tune to clean octaves and specially unisons.

You wrote "> 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>"

But I say OK for pitch, but for unisons, everybody can hear them
howling. Before a concert, if you have time at all to clean the unisons,
you should be fine.

Marcel Carey, RPT
Sherbrooke, QC

> -----Message d'origine-----
> De : pianotech-bounces at ptg.org 
> [mailto:pianotech-bounces at ptg.org] De la part de John M. Formsma
> Envoyé : 10 février 2007 22:26
> À : Pianotech List
> Objet : 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
>