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MMD > Archives > January 1997 > 1997.01.26 > 08Prev  Next

Re: Switched-off Keys
By Karl Ellison

I wrote in Digest 97.01.25, "... by decoupling the keyboard you remove mass that the striking pneumatic has to accelerate when it plays ..."

This is wrong, at least on my piano. I didn't look at my action before I sent this out . Rob DeLand's comments on this subject made my light bulb go on.

Upon inspection of my piano (Autopiano), the striking pneumatic only accelerates the upper part of the action, from the wippen on up. An unlocked key resting in the keybed is balanced such that when the upper action is moved, the weighted key rocks on the balance rail key pin to follow the moving wippen; this key part is all done by gravity.

By not locking the keybed, the resistance part comes when the note stops playing, and the returning action moves back to it's resting position. If the key has moved with the playing note (unlocked keybed), the entire action (key included) has to return to home base resting position. More mass = slower action, thus Rob Deland's assumption that a faster repeating marimba roll (barf!) will play correctly.

My player never "sees" the mass of the key, in the locked or unlocked mode.

Karl Ellison - Ashland, Massachusetts U.S.A. -

[ In most player grand pianos the pneumatic pushes upon the bottom
[ side of the key, at the rear, and so the key must move when the
[ player is operating. In this case, yes, key friction and key mass
[ greatly affect repetition, especially at low pressures. -- Robbie

(Message sent Sun 26 Jan 1997, 13:09:33 GMT, from time zone GMT-0500.)

Key Words in Subject:  Keys, Switched-off

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