Seasonal pitch change: was -- Long term pitch drop, was: Type O

[PAULREVENKOJONES]

In a message dated 03/03/07 20:57:44 Central Standard Time, rnossaman at cox.net writes:

> Ron: 
>   
> Certainly the dimensional changes you suggest would create a pitch 
> difference, but what about the not so inconsequential friction systems 
> of the front scale: bearing cloth, counterbearing bar, agraffe or capo, 
> etc. 

The friction levels of the front scale are usually just that - 
relatively inconsequential compared to that at the bridge. 
They're inconsequential compared with lots of things which doesn't make them per se inconsequential when it comes to the string "rendering" past them; the friction exists and is eminently measurable. My question stands. Could the "couple of thousandths" move sufficiently and in such "even" patterns past those friction points and create the various and varied effects we find in piano pitch change? 




>Would the "couple of thousandths" translate into real pitch change 
> in the speaking length? 

It does for me. Do the math, and decide for yourself.
Done the math in many other contexts. Calculating frequency changes by thousandths alone is not the question; the question was asked in the context of friction and string movement past friction points.



>Would it account for the predominantly middle 
> range changes we experience? 

Which predominantly middle range changes are these? I see low 
tenor, killer octave, and high treble changes in varying 
degrees, typically in that order, though the high treble 
sometimes surprises me in some pianos. The middle range is 
relatively stable in comparison.
I agree and have also experienced wide variations from tenor to high treble, but as many times as not in opposite directions: the tenor drops and the high treble goes higher. If there is any consequential pinblock movement, which I'm not denying since I have no data (nor do you on this mainly speculative point), this would suggest "twist" in the block rather than fore/aft motion. My intuition, which you despise, still pulls me in the direction of bridge/soundboard movement. Isn't it interesting that the bass in most of these varying pitch cases, remains largely stable?



>Would it explain bearing measurement shifts 
> after major pitch change? 

What bearing measurement changes have you recorded, in what 
sections of the scale, with (how) major pitch changes? It's 
about time someone produced something of substance to support 
this premise. 
I could, with a great deal of effort, reproduce the results I recorded years ago, and not to speak for Bob Hohf, but he gave a class on an aspect of this topic at a meeting several years ago, demonstrating measurable bearing changes in a range of strings on either side of a unison which had been pitch-changed. In other words, if nothing else, it showed movement of the bridge/soundboard structure in some direction, and sufficiently to measure with even the gross tools available (bubble gauges, etc.). This doesn't mean that there might not be a combined motion of all wood elements including the pinblock. I'm not denying your conjecture, just asking questions as they seem to make sense to do. 



I'd love to hear Jim Ellis chime in on this. 
>   
> Paul 

Then you'd better cross post to Caut. He doesn't read Pianotech.
My sentiment was out of respect for Jim, Ron. 

Ron N 
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