String coupling.

[Larry J. Messerly]

Has anyone considered that this area of the soundboard may be the most
flexible and that the single string of a unison does not have as much
effect on the bridge as all three pulling the bridge up and down
together.  

This would make the string "think" it is longer as the actual pivot point
of the string moves from the bridge pin to behind the bridge pin.  

Larry Messerly
> 
> Alright Roger, gang, I tried it just moments ago, with the back 
> scale open,
> on a half dozen unisons in the killer octave. In every case, tuning 
> each
> string of a unison as perfectly as I was able to the Tunelab 
> display, the
> unison did indeed drop when all were sounded together, just like you 
> said.
> Also in every case, the unison sounded rougher than I can tune it 
> aurally.
> Touching up aurally, the unison pitch drop disappeared again, or was
> greatly reduced. Checking each string individually against the 
> display,
> they weren't precisely the same anymore, but the unison as a whole 
> was on
> pitch and sounded good. 
> 
> Why?
> 
> Right or wrong, I think it's because there's no reason to assume 
> that the
> partial structure of all three strings in a unison is identical, and 
> they
> in fact aren't. Matching one particular partial of all three strings 
> to a
> common pitch doesn't guarantee a "tuned" unison, because a unison 
> most
> probably can't be "tuned" in the first place because of the partials
> mismatch. It can only be optimized at "minimum garbage". When the 
> fifth
> partial of one string is slightly more prominent or off pitch than 
> the
> measured partial, and the fourth partial of another is doing similar 
> things
> against the eighth partial of the third, the tuner aurally finds the
> subjective optimal balance, where the ETD is quite satisfied with 
> the
> chosen partial(s) match, even if the unison stinks. This is probably
> important, but it's not the whole phenomenon, since it can sometimes 
> be
> nullified by aurally tuning the unison. Then again, it just occurred 
> to me
> that it could indeed prove to be the whole phenomenon, with 
> something
> similar coming from an open duplex, front or back. It may be that 
> you
> simply don't have control of the duplex segment pitches necessary to
> achieve the aural balance you can in the speaking segments. It might 
> be
> just that simple, or I just don't know how to run Tunelab.
> 
> I realize that this seems to be a gruesomely complicated thing, and 
> at this
> point I'm trying to identify and assign helmets and lockers to all 
> the
> major players and keep the endless disconnected details in the cheap 
> seats
> until they can be fitted into a basic premise or two, which I'm 
> currently
> groping for. In the end, who knows? Time will tell, and the quest is 
> young.
> I'm still on the first piano, and we haven't even gotten to the 
> argument
> stage yet.
> 
> Later, 
> Ron N