I would just like to second the motion by John Tuttle that solenoid
players may not ultimately be the way to go.  The major drawback to
pneumatic players is the pump and motor arrangement.  I would suggest to
anyone wanting to design the world's best (affordable) reproducer to
start there.  Design a vacuum pump that is small, quiet, and capacious.
After that, the rest of it is going to be relatively easy.

Although solenoids play the salon-style music (background) very nicely
while you have a bite of lunch or a martini, they will heat up fast
trying to play Rachmaninoff or Wagner, and their power range is limited.
So also is their ability to play extremely soft, or so it seems to me.
It's amazing how those solenoids can play as well as they are able to do,
anyway, after looking at their size and heat sinking.  But in my opinion,
the best of both worlds would be a pneumatic action which can be con-
trolled both by rolls and MIDI.  And in the MIDI arrangement, any roll
format could conceivably play well on a any given pneumatic reproducer.

When piano manufacturers built player pianos, it was very important to
them that every single part on that piano had approximately the same MTBF
[Mean Time Between Failure], i.e., the same failure time on the average.
Such is not the case in electronic players yet.  I have heard that five
years is the average life of the tape transport.  Ten for about
everything else.  So if those figures are correct, maybe we should just
keep them shined up and play them for company so they'll last longer.

Craig Brougher