The first electronic drum machine was built by sonic pioneer Léon Theremin and musical theorist Henry Cowell in 1931. The Rhythmicon (or Polyrhythmophone) used valves, spinning cogwheel discs, and electric photoreceptors to produce rhythmic subdivisions based on the harmonic series.
Samplers, such as the Chamberlin, were developed in the 1940s and 50s, their tape-reel segments warbling to the press of organ keys. Further pioneering work in the 1980s on such iconic instruments as the Roland TR-808 and Akai MPC60 set the standard for rhythm sequencing and sampling. Modern drum machines and samplers may be digital or analogue, hardware or software, and controlled by keys, pads, or indeed any MIDI/USB compatible device.