Today I examined a specialized "music box" that once made
music for an ice cream vending truck. It is housed in a simple
plywood box about 7 x 8 x 9 inches. Outside the box, all that's
visible is a 1/4-inch audio connector and a 4-3/4-inch diameter
wood pulley with a groove for a 1/8-inch O-ring drive belt.
On the side opposite the drive pulley is the end of a 1/4-inch
shaft with milled grooves, secured by a spring latch, as for
selecting up to 5 different tunes of one revolution (although
only one song is pinned).
Inside the box is a tiny 10-key carillon, operated by a rotating
wood cylinder with steel pins to lift the mallets. Each mallet
is powered by a piano-wire spring. Behind every steel chime bar
is a magnetic pickup coil much like that for an electric guitar.
The tiny mallets play the "Good Humor" ice cream jingle,
repeating the tune approximately every 9 seconds.
Stamped inside in several places is "West Coast Organ Co.,
Los Angeles, Calif." The firm was also known as L. Bacigalupi
Organ Co.; see http://mmd.foxtail.com/Pictures/bacigalupi1.html