[CAUT] Sostenuto

[Jerry Cohen]

Last night I tuned a Yamaha CFIII 9ft. grand for a concert. This is a new
piano and is on loan from Yamaha Artist Services. The pianist was having an
occasional problem with the sostenuto which made a loud slap under the
following condition:

First the sostenuto pedal is depressed holding the appropriate notes. With
the sostenuto still depressed, she would use the damper pedal. So far no
problem. Then with the damper pedal still depressed, she would release the
sostenuto pedal. Finally when the damper pedal is released, a loud slap
occurs.

What I found is when the sostenuto pedal is released with the damper pedal
engaged, the sostenuto blade cannot rotate back to its rest position because
the spring tension from 70 sostenuto tabs collectively are locking the blade
up. Finally when the dampers are released, the blade can rotate back, along
with the free falling linkage which makes the slap. With only minutes before
the start of the concert, I could not try any adjustments.

Last February, Kent Swafford presented a very detailed check out for the
sostenuto system, and he described exactly this condition which I quote.


"Depress sostenuto pedal. While continuing to hold the sostenuto pedal  
down, depress the damper pedal. While continuing to hold the damper  
pedal down, release the sostenuto pedal. The immediate flipping of  
tabs should make a noticeable sound as the blade returns to its rest  
position. (If the blade is held too tightly in its mounting brackets,  
there might be an inappropriate delay in the return of the blade to  
its rest position. The tabs should not be able to keep the blade from  
returning to its rest position.)"

I have a few questions regarding this condition.

Since the blade could not return to its rest position with the dampers
engaged, does this mean the sostenuto rail was positioned too far in, thus
overlapping too much of the tabs?

>From a piano performance point of view, is this a "legal" use of the
sostenuto? After all, even if the blade could return to rest, there would
still be the ugly noise from all the individual tabs flipping.

I tune this piano every week, so next week I could have a chance to make
some adjustments. In every other way (I think), the sostenuto was working
perfectly.

I would appreciate any advice.

Jerry Cohen, RPT
NJ Chapter