It is possible to repair and refit Rollmonicas.  Their cases are brittle
but repairs can be made with epoxy and cyanoacrylate glues if done
properly.  The main problem seems to be the cork gasket which dries out.
In the case of a harmonica transplant, even a good cork gasket would not
likely match both parts.  Also the weakened old plastic would not have
enough strength to compress the gasket without breaking.

The solution is to make a new gasket out of 1\16" closed cell neoprene
foam.  It has just the right properties to seal without breaking parts.
You might have to relocate the brads which hold the harmonica in place to
accommodate the difference in thickness of the new and old gaskets.  The
case gasket also hardens and usually has to be replaced, especially if
the case has warped a little.  Pure surgical grade latex tubing works
well.  It can be obtained from laboratory supplies and some hobby shops.

The harmonica itself is not easy to repair.  They were thrown together
rather quickly with no regard for future repair.  The brads that hold
them together are likely at different angles and all bent.  They should
be eased out very gradually and identified to allow them to be put back
in the same position.

If reeds are missing or damaged you need to be a real pro to do it.  If
the reeds are even a little bent out of the ideal location in the plate,
they will sound unevenly or not at all.  Careful coaxing can get them
even if they are not damaged.  You can make a little cup to fit over the
read, connected to a piece of tubing, to test the reads without putting
the thing back together each time.

There are little valve like flaps that always seem to be curled and dried
up.  I have replaced these with light weight motor cloth but have no idea
what their function actually is.  They don't really seem to be capable of
acting as valves which they appear to be.  Maybe the original material
had just the right stiffness to act as a valve and may have allowed the
Rollmonica to work as well under suction as under pressure.  Any ideas
about what material to try or what the little things really are?

The things are real cute, but unfortunately most of the "music" is
terrible.  I'm sure arranging for a 12 note "instrument" is not an easy
job.

Spencer Chase