[Ghosts of impedance past, and yet to come]

[Marc Damashek]

Ron:

This sounds a lot like a phenomenon described in the 1978[?] Scientific
American piano article (grand piano harp on the cover). The crux of it was
that the horizontal components of neighboring strings communicate with one
another directly across the bridge, effectively becoming nonlinearly coupled
oscillators. This is a situation in which (sometimes chaotic) mode-locking is
common, with the cycling of one of the oscillators being captured (steered,
entrained) by the other. It has been studied in some detail in biological
(small groups of neurons) and optical (laser mode-locking) systems, among
others. Not simple, not necessarily reproducible in detail, and hard to
predict.

Marc Damashek
Hampstead, MD


Ron Nossaman <RNossaman@KSCABLE.com> wrote:
> Hi Gang,
> Anyone remember my fevered speculations about the possibilities of the
> reported pitch drop from a single string to a two or three string unison
> possibly being related to the soundboard/string impedance match/mismatch?
> Well, it just got stranger.
> 
> Tuning the Kimball grand I'm finishing up, I set Tunelab going so I could
> watch what a unison's pitch did as I progressed. I spent most of my time in
> the top half of the scale. Some unisons dropped slightly, some stayed the
> same, and some climbed in pitch as the second and third strings tuned in.
> It was about an even three way split on probability, with no obvious order
> or grouping as to position in the scale. The changes in the timing of the
> attack pitch climb and drop back to dwell pitch were every bit as erratic
> as the dwell pitch change. Some unisons that hadn't changed as the second
> and third string tuned in, tended to climb slightly in pitch in decay. Some
> dropped. 
> 
> Thinking I might have some control of the process by where I centered the
> tuning of that second string, I played with it a bit within that area just
> sharp or flat of dead-on to the first string - where you can wooly up the
> attack a little without leaving a noticeable roll in the unison. Some
> unisons seemed to be slightly steerable, some not. My favorites were the
> unisons that went sharp as the second string tuned in, even when the second
> string was still a beat low. 
> 
> In most cases, the addition of the third string took the climbers a little
> higher, the droppers a little lower, and left the non changers non changed.
> The only reasonably dependable effect I found was that the attack phase
> pitch climb  tended to shorten in duration with the addition of each
> string. It was interesting watching the attack phase of the unisons that
> climbed in pitch. The single string envelope profiled about like that of
> any other single string. Adding the second string, the attack pitch climb
> seemed to be less than with the single string, but rose to maximum dwell
> pitch in a second or so.
> 
> So far, no answers, just more and different effects than others are
> reporting. I'll tape off the back scale and play with it some more this
> weekend. That will probably just add another layer of unaccountable
> weirdness, but I might get lucky too. 
> 
> Later, 
> Ron N


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