humidity and unisons

[Fred Sturm]

Newton Hunt wrote:
> 
> > Are soundboards installed badly in all pianos?
> 
> Probably. Too few are installed in strictly controlled
> conditions and many are just not designed properly.  As Del
> about this sometime when you have lots of time.

I'm very skeptical that this could explain the unison/humidity
phenomenon. At least my imagination doesn't see a potential connection

> 
> Bridge roll is determined by putting a thread along side the
> longest rib and observing the gap between thread and board.
> This can be done in several places.  If the gap is a nice
> curve then there is no roll.  If the gap closes on one side
> of the bridge then there is a problem which likely started
> at installation.

I shouldn't have used the term "bridge roll," as I didn't mean to
describe this failure of the bridge/soundboard. I just meant that the
movement of the bridge/soundboard ended up with the bridge canted
differently in relation to the string plane, reversible when the
humidity shifts back in the other direction.

Fred Sturm