Martha,  Your disc toy project sounds interesting! [ Digest 971206 ]

Another idea that was once used is a wide plastic belt in which wooden
pegs are inserted through holes.  It was called the Kariola (National
Scientific Products Co., Chicago, IL), and the pegs trip (L-shaped)
levers which upon their release strike (by gravity, if I recall) a
chime, like a xylophone sound.

It used several "sets" of holes which were identified by symbol, each
making a tune when filled with pegs.  The belt rotates by a simple
crank.  The only design weakness appears to be that the belts stiffened
over a few decades.  :-)

Give me a holler if you'd like more details.

Todd Augsburger