[ Ref. 130504 MMDigest, "Seek Multiplexer Unit for O-roll
 [ Orchestrion," by Jeff Bridges

I think the terminology may be incorrect as no original Coinola O-roll
machines used a multiplex system.  They did, however, use lock and
cancel units.  One hole in the roll will turn an item on and a second
hole then turns it off.

The xylophone is one example where a hole turns it on and a second
different hole turns it off.  Coinola had a unit that had the valve
turn on with a lever connected to a pouch that held the valve up in the
"on" position.  Another valve controls a small pneumatic that can push
the valve down into the "off" position.

Multiplex units are found in a Seeburg KT Special or E special.  This
unit moves a slide that changes one tracker bar hole to another hole
so that one hole in the tracker bar can be used to do a different
function, such as change from snare drum beater to wood block.

Wurlitzer used a multiplex device that would allow two holes in the
tracker bar, when both holes are punched at the same time, to turn on
an instrument that when the holes are used by themselves would turn
on something else.

Peerless used two holes punched together to turn the piano off.  There
was a lever in the keybed that kept the two notes from playing.

Don Teach
Shreveport, Louisiana

 [ MMD articles about lock and cancel systems are indexed at
 [ http://www.mmdigest.com/Archives/KWIC/L/lock.html 
 [ -- Robbie