I'm intrigued by Andrew Barret's interest in building a small crank
organ that apparently is to blow the pipes directly from the paper
roll's holes via the tracker bar, without intervening "amplification"
by pouches and valves.

Is this possible?  Has anyone done it?  It should be possible, by
enclosing the entire spoolframe and applying air pressure much higher
than would actually reach the pipes, due to flow losses in the tracker
bar holes and the tubing.

A complication is that the smaller pipes, which use less air flow,
would receive a higher percentage of the spoolbox pressure than the
large pipes.  This could be allowed for in the pipe voicing, but it
would be much simpler to interpose adjustable throttle valves in the
air lines to the smaller pipes, and adjust these to equalize the
pressure across a normally-voiced set of pipes.

But maybe the reason few "monkey" organs were made this way is that
using the paper holes as valves gives a slow opening and closing of the
air passage, compared with the snappy on-off action of an intermediate
relay valve.  On reed organs, of which many were built this way, the
effect is just to slow down the attack and release of the notes -- but
on pipes it may give a comically "droopy" effect at the start and
finish of each note.

Some early American band organs use a pressurized spoolbox, but only to
operate the relay valves which blow the pipes.

For the record, I have a basket-case Dutch miniature book organ that
blows the treble melody pipes directly from the keyframe pallets (but
uses pouch valves for the accompaniment bourdons and bass pipes).  But
since the key fingers snap through their holes in the book music very
quickly, at least the attack side of the notes should not suffer.  If
I (or a kind soul who would buy this organ from me) gets it playing,
we shall see.

--Mike Knudsen