Sam,  You surely are not the first person to do it this way.  The most
simple was is to take a piano stack and mount an electronic keyboard
above it, upside down.  There is a fellow in New Jersey who is
recording all the Duo-Art rolls this way.  The player action would
simply push the keys and the keyboard  puts out sound and/or MIDI.

Perhaps a more straightforward way would be to mount a microswitch
on each pneumatic and run the resulting contacts into a MIDI encoder.
I do this for a barrel reader and use an Octet MIDI interface box
between the switches and the computer.  Works like a charm.

I have also made a bar of switches to go into a player piano.  A friend
has it now and uses it to play a pipe organ in the next room, but you
could just as easily run the wires to a MIDI encoder device.  Very
simple.  You could use individual microswitches but I just used fine
spring wire that was pushed against a grounding bar by the back end of
each key.

Craig Smith

 [ At http://mmd.foxtail.com/Tech/index.html is a small collection
 [ of useful information and articles related to building a roll
 [ transcriber system.  See the topics "Music Roll Readers" and
 [ "MIDI Control".  -- Robbie