[pianotech] Tuning stability problem

[Don Mannino]

Lim,

This is caused by multiple factors as others have mentioned, but fortunately
they can be resolved with tuning technique and a little time.

The first is that the strings are not equalized in tension over the bridge.
Especially with new pianos with everything going flat from the new wire, the
tendency is to pull it up into tune and then  settle the pin a little.
Unfortunately this can leave the back scale tension low.  By pulling it
quite sharp and pounding it down you will pull the strings across the
bridge.

In addition, this technique will settle the tuning pin in a position that is
not twisted in the sharp direction inside the pinblock.  These undersized
pins tend to twist a lot during tuning, so by pulling it up 15c or more you
are making sure the bottom of the pin has spun into position, then you
settle it down again into a stable location.

So in the technique you saw Otake-san use, the pounding wasn't doing all of
the pitch lowering.  You pound to get the string to move over the bridge,
but at the same time you settle the pin back into a stable position.

Once this hard tuning job is done and the strings and pins are settled, you
don't have to pound it like this every tuning.  In my experience you do this
once or twice on a piano, and it will be stable after that unless humidity
changes are large.  In that case you might need to do a pin-wrestle job once
a year or so.

Finally, these large Kawai models have pretty substantial friction under the
capo bar.  This is done intentionally for tonal reasons, but it means that
the tuning technique is different compared to a low friction piano, or
compared to a piano with springy pins that have no plate bushing.  So the
technique for these pianos is different - but once you get used to it, it
becomes automatic like any tuning technique you do regularly.

The trick for the final stability is to do the last small unison adjustment
UP to the final pitch instead of down.  With these pins that don't spring
much and the friction in the strings, this will tug the string through the
capo and leave the tension in the front duplex high, leaving the string very
stable.  If you settle down to final pitch for unison tuning, the front
duplex will be quite low in tension compared to the speaking length, and on
the first loud passage the unisons will be out.  If you settle up to the
final pitch, the unisons should stay.

Don Mannino RPT

-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of limhseng at gmail.com
Sent: Tuesday, September 21, 2010 6:34 PM
To: pianotech at ptg.org
Subject: [pianotech] Tuning stability problem

Hi
When a grand piano sits on a Y type trolly, will there be tuning stability
problems? I tuned a SK7 which sits on a Y trolly and I have a hard time on
the octaves and unisons from key 55 onwards.

Regards
Lim
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