Thanks to the tip posted a day or so ago, I checked out the Web site
of the British business that sells small circuit cards that receive
MIDI and drive appropriate electromagnetic valves or whatever you
need.  John's "jw Electronics" is at
http://www.jwelectronics.free-online.co.uk/

The news is encouraging: for $86 US you get a 2" by 8" card with 32
note outputs.  I'm sure that's because 32 is a power of 2, but it
happens to be just enough to drive a Raffin monkey organ with one left
over for the conductor figure!  The owner of this enterprise will even
custom program your board to handle less than fully chromatic scales,
and map several notes onto one output (as to send sharp notes to their
natural pipe valves) if desired.  I think his price even includes
shipping!

Several boards can be chained together for more notes, so two or three
would handle the largest reed organ (one manual).  Larger ones are sold
only to special trade customers or are under development.  Also
available is a 28-note version with four stop-select outputs.

With a set of little valves from Ragtime Automated Music spliced into
the tracker bar tubing, one of these boards and a 12-volt battery would
give you a truly expanded repertoire.  And you can arrange your own
music!

Let me remind purists that splicing electronic valves into tubing is an
easily reversible modification -- probably easier than filling in the
holes where you screwed down the MIDI board :-)

Mike Knudsen