From Wikipedia:

The Rhythmicon—also known as the Polyrhythmophone—was the world’s first electronic drum machine (or “rhythm machine,” the original term for devices of the type).

In 1930, the avant-garde American composer and musical theorist Henry Cowell commissioned Russian inventor Léon Theremin to create the remarkably innovative Rhythmicon. Cowell wanted an instrument with which to play compositions involving multiple rhythmic patterns impossible for one person to perform simultaneously on acoustic keyboard or percussion instruments. The invention, completed by Theremin in 1931, can produce up to sixteen different rhythms—a periodic base rhythm on a selected fundamental pitch and fifteen progressively more rapid rhythms, each associated with one of the ascending notes of the fundamental pitch’s overtone series.