a mechanical musical instrument consisting of a case containing a bar with tuned steel teeth that are struck by pins or projections so arranged on a revolving cylinder or disc as to produce a certain tune or tunes
See music box in American Heritage Dictionary 4
noun
A music-making device consisting of a housing or box enclosing a sounding mechanism, especially one in which a row of tuned steel teeth are plucked by pins set in a revolving cylinder to produce a melody.