String coupling.

[Roger Jolly]

>
>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?

Hi Ron,
           At least you restored my sanity, well the little that I never
had. I have also noted similar results as you have indicated. 
With a new set of hammers, very carefully mated to the strings, I have
noted that the partial pattern is very different on the centre string, by
single straight line needling up the cup line to pop the cup and then re
mating, similar patterns were obtained on all 3 strings.
The ETD unison will now both show  and sound correct. The only conclusion
on my part is that the ear is a remarkable instrument,  in that it can
compensate in a manner that is amazing, when dealing with slightly false
beats and mis aligned partials.
The stiffness of the bridge due to notching, (gut feel tells me, enters the
picture) although I have no proof in this regard.
The quest continues.
Please pass the straight jacket.
Roger

Roger Jolly
Saskatoon, Canada.
306-665-0213
Fax 652-0505