Andy,  You suggest a MIDI strip connected to Simplex pneumatic.  I do not
believe that would be a workable system.  It would work, but it would be
very sluggish compared to the system used by one of the Organ players or
Photoplayer systems.

These systems consisted of several decks containing a pouch board with
(approx.) 1.5" pouches all in one row.  The board forming the top of the
chest had one common bus, usually a positive common, across one edge
running the length of the board.  At each pouch location were two gold
plated wires (one is a spare in case of breakage) that went most of the
width of the board to cross the common.  There was generally 1/8" gap
between the feeler wires and the bus.

There was a small spacer sitting on the middle of the pouch and either
glued to it or hinged out over it.  When working, the pouch raises the
spacer which pushes on the center of the feeler wires which rise 1/8" to
touch the bus.  They then continue up slightly beyond the point at which
it fires the contact in order to wipe the feelers against the bus wire
and keep the contact point clean.  I would suggest diode suppression to
prevent arcing and burning of contacts in a modern system, but the wiping
will keep dirt and tarnish off the contacts.

This system was used in Welte Philharmonic Organ players, and most of
the others.  Some had small pneumatic relays if they had large numbers
of wires to contact as in a Photoplayer.  The organ players only needed
to make the equivalent of one manual contact, which in turn fired the
relay system.

I have a Link photoplayer relay which I plan to get running someday
for the very purpose you suggest.  I also have a Moeller Artiste pipe
organ player that I could tear into to copy.  If you wish to come visit,
I would be happy to show you these systems.

D. L. Bullock   Piano World   St. Louis

 [ Editor's note:
 [
 [ The nicest pouch-switch design I've seen is a Moller unit restored
 [ by Ron Sanchez for the Charles Davis Smith's concert organ in 
 [ Monrovia CA.  As I recollect, the pouch has cemented to it a tiny
 [ silver bar, which completes the circuit between a bus bar and a
 [ similar contact for each key.  Sanchez noted that the Moller organ
 [ was designed in the late 1920s and incorporated many innovations.
 [
 [ I checked in the Bowers' Encyclopedia to see if "photoplayer"
 [ should be treated as a trademark, and capitalized.  The answer:
 [ no.  A "Fotoplayer(tm)" was sold by the American Photo Player
 [ Company;  in their own advertising Wurlitzer called the
 [ instrument a "Theater Orchestra" or "Pipe Organ-Orchestra."
 [ Now I'm curious: when did the generic word "photoplayer"
 [ come into use?  Bowers doesn't say.
 [
 [  -- Robbie