I will fall toward the side who believes that the keyboard lock on a
player piano was to prevent youngsters from banging on the keys,
particularly  when the player was playing.

I can understand how someone would feel that decoupling the action from
the keys would speed it up, but Galileo and every physicist I know would
disagree in theory.  You can disprove it to anybody's satisfaction (or
dissatisfaction), if you run a fast, repetitive test roll, like the
25-note repeat test roll which Ampico used to use.  Crank it up on an
upright, both with and without the keyboard lock on.  There is no
difference.  Adding weight does not change the speed of anything which
falls by gravity return.

However, if you have some rather sticky keys, then it will.  So we
are assuming that things are clean and snappy.  Most rebuilders also
understand that keyboardless pianos are no faster in their action
(or slower) than the ones with keys.

Craig Brougher

 [ The expression Craig used, "crank it up ..." is undoubtedly older
 [ than cranking the automobile to start the engine.  I bet that it was
 [ shouted more than 200 years ago, probably in a pleasant German
 [ Biergarten: "Crank it up, Hans!" (in German, of course) ... and the
 [ barrel-organ began playing!  :)  -- Robbie