Ghosts of impedance past, and yet to come

[Ron Nossaman]

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