[CAUT] IRe: Unison drift (was Reading low humidity/seasonal SB failure)

[Dorothy Bell]

> [Original Message]
> From: Fred Sturm <fssturm at unm.edu>
> To: caut <caut at ptg.org>
> Date: 3/2/2006 11:31:18 PM
> Subject: Re: [CAUT] Reading low humidity (was seasonal SB failure)
>For instance,
> we just had a trace of rain last night, first in months. RH rose virtually
> instantly inside the building from 13% to 25%. I know from experience that
> by this evening . . . most of the mid to high treble will have unison
drift with a
> pattern of right string 0.5 cents sharp, left string 0.5 cents flat, etc.

Dear Fred,

I'll bite: what mechanically would make the unison drift with that
particular triplet pattern? I tuned a home piano this morning which was in
exactly that situation after having been tuned at much higher RH five
months ago. Somewhere recently I read that 'if the pitch goes out, it's the
humidity; if the unisons go out, it's the tech.' I'm certainly willing to
take responsibility for all the griefs of man, but it doesn't make sense to
me that unisons going out in a very specific pattern, in a very specific
part of the piano, would indicate poor hammer technique. When I look at the
piano, though, I don't see what would cause the consistent flat-sharp
changes.  Can you advise? Thanks.

Dorrie Bell
Boston, MA