I have a crazy idea to build a "steam-punked" cart-mounted organ!
In addition to the obligatory big brass pressure gauges, extraneous
clockwork, and excessive bright copper tubing, I think it would be very
cool to feature an automatically operated big brass slide whistle.
I can imagine how to do this with a linear stepper motor (which might
represent an appropriate blending of technology), but it has me
wondering how it was done pneumatically.

The Popper Roland features a slide whistle (or "Swanee whistle", as
they called it) driven from a paper roll.  Could someone explain the
mechanism behind this (or, even better, provide a diagram)?  Is it
controlled by its own portion of the scale on the roll, or is it
playing a melody line on a register?

I can imaging how to set stop points for travel of the slide with
pneumatics, but my imagination is failing me on how to appropriately
push or pull the wire to move the slider from note to note without
some pretty complicated (or at least tedious) coding.

I can imagine using two holes to encode "go left" or "go right", or a
single hole that would encode a "reverse" signal, so that whenever it
was necessary to reverse the direction of travel of the slider you'd
send a signal on that tube to flip a relay.  This would require pretty
careful punching of the roll and would preclude using a standard small
organ scale.

Rather than re-invent the wheel, I thought I'd find out how it was
done before.  Unfortunately Popper Rolands aren't to be found on every
street corner for casual dissection!

Cheers,
Roger Wiegand
Wayland, Massachusetts, USA
http://www.carouselorgan.com/ 

 [ In the instrument I saw (a Roland, I believe), a pneumatic logic
 [ unit determined the highest active playing note in the melody
 [ division and then sent only that single note command to the
 [ slide whistle servo-mechanism, which moved the tuning slide to
 [ a pre-calibrated position.  A simpler system might exist (which
 [ Popper was unable to license from the patent owner).  -- Robbie