Clippard Instrument Laboratory Inc., a maker of pneumatic components,
recently demonstrated a MIDI-controlled six-string guitar that plays
33 notes using 62 air cylinders and 62 pneumatic valves.  Short
videos of music are at  http://www.youtube.com/watch?v=qytBWQDgAGU 
and http://www.youtube.com/watch?v=Hwf-ndRSwPc 
and http://www.youtube.com/watch?v=GymQmYM_4T4 

A description of the pneumatic player system is presented at
http://www.youtube.com/watch?v=pEgwoB9nlJ4 

Thanks to Bill Chapman for the tip!

Robbie Rhodes, MMDigest