Drifting Unisons

[Fred S. Sturm]

Jon Page wrote:
> 
I always thought it
> was one of those mysteries of nature.
> 
> Still do,
> 
> Jon Page
> 
	I agree with you, though I am cursed with a mind that wants to puzzle 
out at least some mechanical conceptualization so I don't have to rely 
on "gremlins" (though there are certainly times when gremlins seem the 
best explanation). I'm glad that several others have verified what I 
have claimed to be a "tendency" or "consistent pattern," because there 
are so many exceptions, I sometimes wonder if what I was so sure of 
yesterday (when all the pianos I tuned fit into a pattern) was merely an 
illusion (today there doesn't seem to be any pattern at all). Obviously 
there are many many factors involved, each causing a result, some in 
conflict with each other. I think this is a very dynamic activity, and 
it seems that the clear patterns emerge when there has been a large and 
consistent movement of humidity in one direction or other. When humidity 
has been unsettled, or has generally gone one way, but is now in the 
process of moving in another, all bets are off - haywire, patternless, 
is the best way to describe the results.
	There is a practical side to all this observation and trying to find 
patterns. Beyond being able to predict what you may find, and being able 
to communicate the possibilities to performers and piano owners, it is 
helpful to be aware of the unison phenomenon when doing major pitch 
changes using an ETD. In fact, this is where I started noticing 
patterns. I tune, generally speaking, with one mute, left to right. (By 
the way, I have reversed this several times to see if it made a 
difference in how unisons behaved. It did not, in my experience). When 
reading a pitch to let my SAT calculate pitch overshoot, I first measure 
the left string, then move the wedge and see if the right string is 
close to that pitch. If it is far different, I measure it, and use a 
value about half way between as the input. Results in much closer pitch 
change results after one pass.

Regards,
Fred S. Sturm, RPT
University of New mexico