The Rhythmicon—also known as the Polyrhythmophone

The Rhythmicon—also known as the Polyrhythmophone—was an electro-mechanical musical instrument designed and built by Leon Theremin for composer Henry Cowell, intended to reveal connections between rhythms, pitches and the harmonic series. It used a series of perforated spinning disks, similar to a Nipkow disk, to interrupt the flow of light between bulbs and phototoreceptors aligned with the disk perforations. The interrupted signals created oscillations which were perceived as rhythms or tones depending on the speed of the disks. Although it generated both pitches and rhythms, it has often been described as the world's first drum machine.