Unstable Yamaha C7

[Paul McCloud]

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Mark:
    I think your problem is definitely the temperature fluctuation.  I always ask the customer to close the door/window to eliminate any breeze over the piano.  I also ask them not to change any climate control that they normally use when I'm not there.  (Sometimes they'll turn the air cond. to make me comfortable).   I've found that any change in temperature around the piano affects my tuning, and the strings are vulnerable to temperature changes especially when the cabinet is opened for tuning (uprights).   
    Hope this helps,
    
    Paul McCloud
    San Diego


----- Original Message ----- 
From: Mark Dierauf 
To: pianotech@ptg.org
Sent: 06/16/2004 6:28:04 PM 
Subject: Unstable Yamaha C7


I take care of an older Yamaha at a recording studio that has a tuning instability problem that I’ve never encountered on any other piano – the pitch fluctuates by as much as 3 or 4 cents over the course of only a few minutes. It took me quite a while to realize that this fluctuation ran in sync with the forced hot air heating system. Now that it’s summer, the air-conditioning from the same vents is having the same effect. The piano has a complete DC unit installed with a bottom cover, is tuned at least 20x annually, and is very pitch-stable in the long term. It is not located in direct sunlight and the temperature doesn’t vary much, certainly not within seasons. In the winter there is a humidity control system adding moisture through the hot air ducts. The studio is in an old New England barn that had several hundred thousand dollars worth of renovation, and so is very well finished and insulated, but in the time that it takes me to work through the temperament the first notes tuned have already moved substantially. Once after chasing the pitch all through a tuning I repeated A4 for several minutes and watched the pitch rise about 2 cents above the starting point then fall about 2 cents below. This cycle kept repeating as I watched. Has anyone ever seen such a problem? Did you find any solutions?
 
- Mark
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