[ Robbie remarked in 051002 MMDigest:

>[ Andrew Barrett suggested to me that a small pouch, controlled by
>[ a tiny electric valve, could push the sticker of the barrel organ.
>[ This method might incur the least added weight of the alternatives.

I agree.  But finding a "tiny electric valve" has been a problem.
To control my Raffin organ, I had to use Peterson or OSI valves,
which are designed to blow an organ pipe.  These are way over-sized
for opening a tracker bar hole to operate a pouch or small pneumatic,
but they are what is available.

Smaller alternatives are the in-line valves made by Ragtime Automated
Music in California, but people have reported problems with these.
Also, the Gerety-Chase valve blocks would be suitable, if they can
be purchased separate from their electronics (which are intended for
fully chromatic pianos, not nearly-diatonic barrel organs).

I have made a prototype of a smaller electromagnetic valve that an
amateur can build, though I'm not fully satisfied with it yet.  Anyway,
the market for a small valve suitable for tracker bar tubing is still
open.

I just now remembered seeing a Welte orchestrion -- the classic type
with the radiating trumpets -- whose barrel keyframe had been fitted
with electromagnets to permit electronic control.  The magnet and
armature design was similar to the Peterson/OSI organ pallet valve
design, only somewhat larger.  The armatures were tied into the
"tracker" links from the keyframe to the windchest.  The barrel and
keys were still in place and presumably still operable.

Now, the size, weight, and cost of these magnets would likely be out
of the range for a small barrel organ, plus the battery pack, but the
Welte is a good example of how it can be done.

Joke:
  Q. Why don't barrel organ owners worry about mice?
  A. Because there's no space inside big enough for a mouse!

Mike Knudsen