Hi All,  Well, I'm not ashamed to admit when I'm in over my head.
Paul Rumpf's excellent reply to my questions and his article in
the MMD Archive have proven to me that I'm simply not well enough
educated to actually comprehend 'why' a player piano works.  I suppose
it was also foolish of me to think that it could be broken down into
relatively simple terms that anyone could understand.  I should
consider myself blessed that during the 42+ years that I've been
fixing player pianos, I have always been able to figure out what isn't
working correctly and what I needed to do to get it working again --
without completely understanding 'why' it worked in the first place!

Musically,
John A Tuttle
Player-Care.com
Brick, New Jersey, USA