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<DIV>
<DIV>In a message dated 6/16/04 9:27:49 PM Central Daylight Time,
mark@nhpianos.com writes:</DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid"><=
FONT
style="BACKGROUND-COLOR: transparent" face=Arial color=#000000 size=
=2>I take
care of an older Yamaha at a recording studio that has a tuning<BR>instabi=
lity
problem that I've never encountered on any other piano - the<BR>pitch
fluctuates by as much as 3 or 4 cents over the course of only a<BR>few
minutes. It took me quite a while to realize that this fluctuation<BR>ran =
in
sync with the forced hot air heating system. Now that it's<BR>summer, the
air-conditioning from the same vents is having the same<BR>effect. The pia=
no
has a complete DC unit installed with a bottom cover,<BR>is tuned at least=
20x
annually, and is very pitch-stable in the long<BR>term. It is not located =
in
direct sunlight and the temperature doesn't<BR>vary much, certainly not wi=
thin
seasons. In the winter there is a<BR>humidity control system adding moistu=
re
through the hot air ducts. The<BR>studio is in an old New England barn tha=
t
had several hundred thousand<BR>dollars worth of renovation, and so is ver=
y
well finished and insulated,<BR>but in the time that it takes me to work
through the temperament the<BR>first notes tuned have already moved
substantially. Once after chasing<BR>the pitch all through a tuning I repe=
ated
A4 for several minutes and<BR>watched the pitch rise about 2 cents above t=
he
starting point then fall<BR>about 2 cents below. This cycle kept repeating=
as
I watched. Has anyone<BR>ever seen such a problem? Did you find any
solutions?<BR><BR>- Mark<BR></FONT></BLOCKQUOTE></DIV>
<DIV></DIV>
<DIV>Mark</DIV>
<DIV> </DIV>
<DIV>I would start by tightening as many plate screws/bolts as possible. Als=
o,
even though you might not hear it, check to make sure the soundboard is tigh=
t
all around the edges. </DIV>
<DIV> </DIV>
<DIV>Wim </DIV></FONT></BODY></HTML>