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<p class=MsoNormal><font size=3 color=navy face="Times New =
Roman"><span
style='font-size:12.0pt;color:navy'>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 =
</span></font><st1:place><font
color=navy><span style='color:navy'>New =
England</span></font></st1:place><font
color=navy><span style='color:navy'> 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?<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span =
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span =
style='font-size:
10.0pt;font-family:Arial;color:navy'>- Mark<o:p></o:p></span></font></p>
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