[CAUT] sostenuto

[Kent Swafford]

What are all the procedures for making certain that the sostenuto mechanism
is ready for concert use? Here is what I have come up with so far.


Dampers must be in good regulation, and all dampers must seat properly. The
damper upstop rail must be regulated perfectly.

Depress damper pedal. While continuing to hold the damper pedal, depress the
sostenuto pedal. While continuing to hold down the sostenuto pedal down,
release the damper pedal. All dampers should remain raised. (This is a more
severe test than depressing each key, then depressing the sostenuto pedal,
and releasing the key to see that the damper stays raised.)

Depess 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.)

Depress and release the damper pedal. Depress the sostenuto pedal; no
dampers should rise. In addition, there should be no noise resulting from
slight contact between the blades and the tabs of any dampers. (If noise is
heard from the blade contacting tabs as the sostenuto pedal is depressed,
you may need to rest your finger on each damper in succession while
depressing the sostenuto pedal to find the damper tabs that are makding
contact with the blade.)

Depress and continue to hold down the sostenuto pedal. Deliver a
double-forte blow to every note that has a damper. All dampers must return
to their rest positions on the strings as each note is released. (This is a
particularly severe test. This test may fail if the sostenuto pedal is not
depressed as far as is possible.)

It appears to me that delivering double-forte blows to notes when the
sostenuto pedal is depressed and expecting them not to sustain is at the
limit of what can be expected from the sostenuto mechanism. I think it's OK
to instruct pianists that they must be certain that the sostenuto pedal is
depressed as far as possible if they expect double-forte notes not to
sustain when the sostenuto pedal is down.


Comments? You'll notice I haven't mentioned how to regulate the blade and
tabs. These are just the tests to determine whether I'm done, that is,
whether further regulation to the balde and tabs are necessary.


Kent Swafford
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