Harmonic Distortion / Overdriving strings?? Noise Question???

[btrout@desupernet.net]

Hi All,

I've run into a customer who has noticed a problem with his Boston
piano.  It's a 6'4" grand.  Playing softly, the tone is good.  But on
louder playing, and rapid repeated playing of particular notes, there
comes an irritating sound from the speaking length of the string.  To my
ear, it sounds like the string is being 'overexcited', or overdriven,
beyond the point of a clear undistorted vibration.  Kind of reminds me
of what happens when you overdrive an amplifier and hear the sound
distort.  On the piano it tends to sound like a zing/ring.  (This is
like trying to tell a person who has never been sighted what a rainbow
looks like!)  Upon further examination, I've determined that the 'noise'
is indeed in the speaking length of the string.  (Blocking out the
duplex etc. has no real effect.)  Also, I've checked on about a half
dozen other pianos for the same thing, all the way from Young Chang, to
Wurlitzer & Baldwin, to Petrof and Steinway.  I was actually able to get
the same distortions from ALL of them!  The Steinway required the most
effort on my part to make it give off this 'sound', but I was able to
get all of them to do it, and over quite a range.  The worst areas on
most all of them was the range starting about an octave above middle C,
and continuing up about an octave and a half, but it was indeed possible
to do this 'overexcitement' over most of the range of the plain wire
strings.

I've not been able to put my finger on this one.  Some thoughts to date
are scattered; hammers are too hard, (voicing seems to help a little,
but it's still there), hammers striking the string in the wrong place,
(haven't been able to play with this one yet), too much bearing, (I'm
not sure how too much or too little bearing would affect distortion of
the sound), poor scale design, (just because it says "Designed by
Steinway", it doesn't necessarily impress me), poor bridge notching,
(the notch does not drop away from the string in such a fashion to give
a good termination point in my opinion, but I don't know what minimums
would be.  I know I notch mine a lot more deeply and distinctly when I
do them.)

I just wondered if anybody had a thought.

Thanks in advance.  (And also, thanks for all the good conversation.  I
just found this list a few weeks ago, and am very happy to be able to
read the conversations.  I've been learning. (Hope it never ends!)

Brian Trout
Quarryville, Pa