[CAUT] Unison Tuning

[A440A@aol.com]

Jim writes:

<< Another thing no one so far has mentioned is the fact that the bridge
itself is NOT rock solid.  When pressure is applied to a bridge pin, it
DOES move - by a microscopic amount - but it moves - and the movement of
one pin will move the next one a little bit.  Wood grain is springy.  I'll
bet that if you very carefully measure (on the same note of the same piano)
unison tuning going from sharp to flat, you will find this effect is not
the same as when you tune going from flat to sharp.  >>

Greetings, 
  Another consideration is that the more flexible the bridge, the longer the 
effective length of the string. A completely immovable termination will stop 
the strings impulse at the point of termination, but a flexible one will allow 
that point to move farther beyond the actual physical termination.  
   Perhaps this is what is happening when all three strings are brought into 
perfect agreement. They lose the stiffening effect of the various out-of-phase 
vibrations hitting the bridge. We know that a slightly "out" unison will have 
more sustain,(Weinreich, again).  
    In effect, the three strings  tuned together gang up on the bridge and 
moves it more than it would if they were not together, thus creating an 
effectively "longer" string.  
So many mysteries, so little brain...

Ed Foote RPT 
http://www.uk-piano.org/edfoote/index.html
www.uk-piano.org/edfoote/well_tempered_piano.html