The great Style "O' roll already has holes in the roll to turn on and
off a set of pipes and a set of bells or xylophone -- no multiplexing
is required.  Adding pipes or bells to an existing homemade player
piano that plays the "O" roll is something that should be left to
someone with experience working on these machines, or a least someone
who has experience with player pianos.  Pipes require air pressure to
operate them as well as a vacuum source to actually play each note in
the pipes.

There are also holes in the roll to operate drums and other percussion
devices, as well several expression holes to control the vacuum levels
for the piano and drums.  The roll also operates the soft pedal or
hammer rail, enabling the "O" roll to offer some degree of expression.
In my opinion one of the greatest pianos playing the O roll is the
Coinola X model with bells.  It is a lively music maker.  Several
Coinola X models seem to appear for sale every year.

Don Teach
Shreveport, Louisiana