I've owned for some years a Concert Roller Organ and about two dozen
cobs.  It works well but needs bellows recovering to cure a shortage of
wind.

This weekend I spotted a Gem Roller Organ with nicely recovered bellows
at a good price, so snapped it up in the hopes of hearing my cobs a
little better.  By the way, the bellows were restored with what appears
to be the "expression cloth" used on reproducing piano regulators.  Since
this is a vacuum organ no stiffeners are used.

As you may know, the Gem and Concert are essentially the same instrument,
but my Concert is tuned a minor third below the Gem.  I guess this
was done to give the encased Concert a fuller sound than the smaller,
open Gem.  It also explains the larger bellows set in the Concert.

But -- my new Gem has a problem.  There are three parts of the mechanism
on the left side that must work together -- the worm screw that advances
the roller on a spiral; the finger that engages the roller in its other
hole (near its edge); and the pin that sticks out from the shaft to catch
a projection on the frame, which sends the whole works back to the
beginning position.

My worm screw and finger agree well, since the rolls play perfectly.
But the projection is off by almost half a revolution, so it resets the
mechanism late (after some horrible cat fights from playing the roller a
quarter revolution) and then causes the first half-turn of the tune to be
missed.

Has anyone ever successfully adjusted a roller organ mechanism?  All
the parts are press-fitted or forged or welded in place, and cannot be
adjusted, except the pin is force-fit into a slot in the shaft.  Any
attempt to adjust anything seems destined just to break something, so
I'm asking before I try.

Long ago I figured out that the adjustable pivots at the bottom of the
works can't really do much of anything, since the cob position is really
controlled from the fixed half-nut that the worm screw engages.

By the way, somewhere I have a major list of rolls from the MBSI
Bulletin.  It's a godsend for identifying rollers where only the number
is legible.

Mike Knudsen