Two of my silly thoughts on the subject of player pianos keys that
don't move when the roll is playing (a subject which I feel has been
done to death!):

1. When I was a kid I learned to play some (rather complicated) pieces
by studying the movement of the keys (so much so that I have the world's
_worst_ fingering technique -- the roll doesn't tell you the proper
fingers to use); and

2. Try making the keys on your Mason & Hamlin grand Ampico, or your
Steinway grand Duo-Art, stop from going up and down when the roll is
playing!

Haha!
Tom Ahearn ("Player Piano Service")

(I do use the key shut-off on upright player pianos when playing fast
tremolo effects, organ and/or "orchestral" arrangements with very fast
repetition.)