Yamaha C7 tuning instability

[Mark Dierauf]

Thanks to all for the responses. I did check the plate screws, but even
my biggest square-shanked screwdriver with a wrench on it couldn't do
more than just crack a few of them a hair. The studio is not large and
there are vents everywhere, so I don't think that it's possible to get
this piano out of the line of fire. The blanket is a good idea for
tuning, but it doesn't help once I'm gone. The engineer usually either
removes the lid altogether or else raises it until it is vertical and
leaning against a piece of foam that he has located on a wall for that
express purpose. I was thinking about trying one of the Edwards wool
string covers, but I assume that this would change the sound (and
volume) and throw off his miking procedure. Has anybody used one of
these covers who could comment? Would a DC bottom cover across the top
of the case (in place of the lid) be likely to help?

- Mark

-----Original Message-----
From: Don Mannino [mailto:dmannino@kawaius.com] 
Sent: Thursday, June 17, 2004 1:24 PM
To: 'College and University Technicians'
Subject: RE: Yamaha C7 tuning instability

Mark,

As you surmised, this problem has nothing to do with the piano, and
everything to do with the air changing the string's temperatures.

The best approach is to move the piano so that it is not in a drafty
spot
during tuning, then move it back when you are done.  Make sure the
studio
owners are aware of the draftiness problem - you can demonstrate it for
them
using your tuning machine easily.  Simple zero out the display, then
'huff'
hot air on the strings while playing it - the display will begin to move
right away.  Well, at least it works well with my unusually large
quantity
of hot air ;-)

This problem could possibly be solved by redirecting a heating vent, or
getting air deflectors for one or two vents that are blowing on the
piano.

A blanket or cover draped over the piano could help during tunings, too.

Don Mannino RPT


-----Original Message-----
From: caut-bounces@ptg.org [mailto:caut-bounces@ptg.org] On Behalf Of
Mark
Dierauf
Sent: Wednesday, June 16, 2004 7:27 PM
To: caut@ptg.org
Subject: Yamaha C7 tuning instability



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



_______________________________________________
caut list info: https://www.moypiano.com/resources/#archives