The Roland TR-909 Rhythm Composer, commonly known as the 909, is a drum machine introduced by Roland Corporation in 1983, succeeding the TR-808. It was the first Roland drum machine to use samples for some sounds, and the first with MIDI functionality, allowing it to synchronize with other devices. Though a commercial failure, it influenced the development of electronic dance music genres such as techno, house and acid house.

A drum machine is an electronic musical instrument that creates percussion sounds, drum beats, and patterns. Drum machines may imitate drum kits or other percussion instruments, or produce unique sounds, such as synthesized electronic tones. A drum machine often has pre-programmed beats and patterns for popular genres and styles, such as pop music, rock music, and dance music. Most modern drum machines made in the 2010s and 2020s also allow users to program their own rhythms and beats. Drum machines may create sounds using analog synthesis or play prerecorded samples.