The most suitable device for amplifying musical boxes is cheap, easy
to make and requires no power.  It is simply a resonant board.  This
can be made from a thin sheet of wood, about 24" x 18", mounted on
a wooden frame for strength, say, around 2" deep.  Very small musical
boxes can make do with a smaller board.

This resonant board can the be placed on any normal table or desk and
you will find that there is more than enough volume for most large
rooms or halls.  Naturally, the musical box must be placed directly
onto the wood, with no cloth or other resilient medium between.

One aspect of musical boxes which is worth noting on any demonstration
is the totally different listening environment compared to today's
musical listening.  Total quiet is required, and this will be of
surprise to today's children.  Using electronic amplification will
remove this important part of any demonstration.

Any average sized musical box will be easily heard in any normal
classroom.  Just try it.  Recently I demonstrated a snuff box in
a 40-foot room and everyone could hear it.

Quiet regards,
Nicholas Simons, UK