Knocking keyframe

[FSSturm@aol.com]

Turning the guide pin 90 or 180 degrees will sometimes take care of the
problem. I think this is what Ken meant by "eccentric" - that the pin is
either bent or wider (less worn) on one side than another. Generally the key
block has a thick cardboard shim glued to the bottom. Removing a layer or two
of the card works initially on new pianos. Once this has been removed,
though, and if turning the pin or replacing the guide doesn't cure the
problem, I don't know what is left, besides the old business card under the
keyframe trick (good to get through that concert).