Programmable mechanical musical instruments, such as the player piano, have a long history. The twentieth-century composer Conlon Nancarrow employed the player piano to realize compositional ideas that would have been impossible for a human pianist. More recently, inexpensive programmable music box kits have inspired several composers to create works expressing mathematical, as well as musical, ideas. I discuss compositions by Vi Hart and Karlheinz Essl and provide resources for using music box kits in the mathematics classroom.