Key to checking,check the key

[Dmsaerts@aol.com]

Dear colleagues:

I read many solutions to the checking problem but I missed a very important
one.  The key is one of the most important parts to influence the checking of
a grand piano.  Since the back check is part of the key.
* An oversize balance bottom hole (read: front to back play in the key) can
cause bad checking.  This is normally unnoticed on the bench, or when the key
is played soft or moderate. But when played hard or fast the looseness of the
key causes the back check to let go of the hammer prematurely. 
*  Bad key bushings in general (read: side play in the key)  can cause the
same.
* Too many paper punchings and thick felt punchings under the balance, causes
the key to "dance" and this in turn causes bad checking when played fast or
hard.
* The NY Steinway which is equipped with the loose half rounds on the balance
rail is more likely to "dance". Not only because of the enormous amount of
paper punchings that sometimes can be found under the half rounds, but also
the thick mushy felt that covers the half rounds.  This in turn creates
something similar to "key flexing," which causes besides limited tone
production when played forte also bad checking.  The half round system is
unfortunately also a rattle producer. (Note to our Lucky overseas colleagues:
Hamburg never introduced this unfortunate half round system. I wonder why?)
* If the key itself also flexes to much (Pratt & Read era for example) it
becomes even more complex to regulate the checking accurately on both moderate
and forte playing.

I read one answer (I think Jim Bryant, FL) that describes the jack getting
pressed against the balancier cushion.  In other words to much after touch or
just not sufficient space available for the jack to maneuver.  I would look to
his suggestion first before any of the others.  Because it's symptoms occur
also when you play forte and don't when you play moderate.

Cyrillus Aerts
Director piano services
University of North Texas