Drum machines are machines which simulate the sounds of percussion instruments, most notably drums. They are useful and widely used electronic instruments, not only in the electronic music genre, but in many other genres as well, and they are perfect replacements for drummers when a session drummer cannot be found.

These machines offer a wide selection of drum lines, carefully and thoroughly sampled in order to be able to reproduce as closely as possible the original sound. They can also be adjusted by the users to suit personal inclinations, using the meticulously mapped out controls, allowing for a range of experimentation with the sound.

Drum machines were first available for commercial sale in the 1960s as a part of organs, and were originally designed to accompany the organist as he played. These early machines were named rhythm machines.

The first successful one was called the Rhythm Ace, manufactured by a company called Ace Tone, which name was later changed to Roland. Other rhythm machines from the 60s include the Rhythm Synthesizer, constructed by Raymond Scott in 1960, and the Bongo Artist, made by a company called Bandito.

These machines were sequencers which has a sample playback or synthesizer component allows the machine to reproduce drum timbres, in addition to other classic percussion sounds. The early machines, due to their technology, did not always approximate the sound of the real instrument.

They used analog synthesizers rather than digital sampling, which is what is used today. A snare drum sound, for example, would be simulated by a burst of white noise, while a bass drum was created using basic waveforms, such as a sine wave. Modern day machines use a number of precise controls to get the exact sound the user is looking for.

These controls include start and stop, tempo, controlling the volume for specific sounds, keys to choose individual drum sounds, and memory to store a variety of programmed rhythms. The majority of drum machines are able to be controlled through MIDI. It is also possible, through MIDI, or by pickups or trigger pads, to generate specific percussion sound modules.

Another aspect of the second by second control is that the drums can be programmed in real time, allowing the user to determine the precise second a beat will sound. In 1980 the Linn LM-1 Drum Computer was created, the first one to use digital sampling. Most of the drum sounds were composed of dual chips which were made at the same time. Each sound was separately tunable with individual outputs, but because of memory limitations, the cymbal sound could not be added.

Drum machines allow artist to program specific drum lines and store them, a skill which has become almost indispensable for drummers. These machines are now widely used in pop and rock concerts, due to their ability to create and retain in their memory unique drum lines.