A Boss DR-202 Drum Machine
Drum machines are sequencers with a synthesizer, sampler, and/or a sample playback (rompler) component that is tailored to imitate the sounds of drums and other percussion instruments. Sample playback drum machines are the most common.
Early drum machines were referred to as "rhythm machines" because they only played preprogrammed rhythms such as mambo, tango, etc. The first rhythm machines were included in organs, in the late 1960s. The first stand-alone drum machine was released around 1970 by a company then called Ace Tone, and was called the Rhythm Ace. This was a preset-only unit; it was not possible to make user-programmable rhythms. A number of other preset drum machines were released in the 1970s.
One of the first programmable rhythm machines, which allowed the user to create their own beats, was the Roland (Ace Tone's new name) CR-78, which came out in 1979. Roland then came out with the Boss DR-55 later in 1979, which was a fully programmable drum machine for under $200. The DR-55 had all of four sounds and memory for only 16 rhythms.
In 1980 the first drum machine to use digital samples, the Linn LM-1, came out. Costing $5000, its distinct sound can be heard on many records from the early 1980s, such as The Human League's Dare and Men Without Hats' Rhythm of Youth. The famous Roland TR-808 came out months later; while the TR-808 did not have digitally sampled sounds, it was a good deal more inexpensive. It was considered a poor man's drum machine.
Drum machines using digital samples were a good deal more popular than the TR-808 in the early 1980s. Its sound only became truly desirable in the late 1980s, about five years after being discontinued. The sounds that are particular to the TR-808 have become pop music clichés, heard on countless recordings.
Because these early drum machines came out before the introduction of MIDI in 1983, they used a variety of methods of having their rhythms synchronized to other electronic devices. Some used a method of synchronization called DIN-synch, or synch-24. Some of these machines also output analog CV/Gate voltages that could be used to synchronize or control analog synthesizers and other music equipment.
Drum machines can either be programmed in real time (the user hears a metronome and plays beats in time with the metronome) or in step time, where the user specifys which notes of a bar a given drum will sound on. By stringing differently-programmed bars together, fills, breaks, rhythmic changes, and longer phrases can be created. Drum machine controls typically include Tempo, Start and Stop, volume control of individual sounds, keys to trigger individual drum sounds, and storage locations for a number of different rhythms. Most drum machines can also be controlled via MIDI.
Stand-alone drum machines had become less common by the year 2000, being partly supplanted by samplers, computer software-based sequencing with virtual drum machines, and workstation synthesizers that have drum sequencing built in. TR-808 and other digitized drum machine sounds can be found on archives on the Internet. However, drum machines are still being made by companies such as Roland Corporation (under the name Boss), Zoom, Korg and Alesis, whose SR16 drum machine has remained popular since the early 1990s.
There are percussion-specific sound modules that can be triggered by pickups, trigger pads, or through MIDI. These are called drum modules; the Alesis D-4 is a popular example. Unless such a sound module also features a sequencer, it is, strictly speaking, not a drum machine.
See Drum machine programming.