This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment I put a bottom cover on a Yamaha C3, large hall, and it helped very = much. ----- Original Message -----=20 From: Mark Dierauf=20 To: pianotech@ptg.org=20 Sent: Wednesday, June 16, 2004 10:26 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? =20 - Mark ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/c1/98/de/55/attachment.htm ---------------------- multipart/alternative attachment--
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