[CAUT] Sostenuto

[Jerry Cohen]

Some of you may recall, last Saturday I had a sostenuto problem with a
performance Yamaha CFIII. The problem occurred if you engage the sostenuto
pedal, then the damper pedal, and release the sostenuto with the damper
pedal still down. The sostenuto rail became locked up until you finally
release the damper pedal causing a loud slap. I received many excellent
ideas from you and Kent even sent me a copy of his January article.

Yesterday I was able to arrive early enough before the concert to diagnose
in peace and quiet. The problem was that the sostenuto rail was positioned
too far into the action cavity, so the blade had too much overlap. If you
engage the damper pedal after the sostenuto is down, the blade could not
rotate past the tabs when you release the sostenuto, because the blade is
too close to the pivot points of the tabs. Thus the blade is locked up until
you release the damper pedal. The loud slap was caused by two parts of the
sostenuto pedal linkage suddenly coming back together.

On this Yamaha, the in/out position is adjusted by bending each mounting
bracket. After making the adjustments, the sostenuto worked perfectly, just
like the textbook (or Kent's article). Now if you release the sostenuto with
the damper pedal still down, you hear all the tabs immediately rub past the
blade. But the noise is quite moderate on this piano. All the other tests
worked perfectly. Nothing was on the edge of just working.

Again, thank you for your help. I learned a lot.

Jerry Cohen, RPT
New Jersey Chapter