A synth for creating drum sounds, which unlike the drum machine, is equipped with drum pads and intended primarily to be played by hand as opposed to sequenced. Drum synthesizers began appearing in the late 1970s with units from Syndrums and Synare; most of these were monophonic units with a single playing surface, limited patch editing capability, and no patch memory. The electronics were usually built into the playing surface enclosure, and since these units were intended to be played with sticks, the electronics were subject to the shock and vibration of playing, leading to reliability problems. The state of the art moved forward substantially when Simmons introduced their SDS-3 system in 1978. This was a four-voice system with four drum pads and the electronics mounted in a remote box. At this stage the drum pads were conventional tomtom drums with sensors attached.
The defining moment for drum synths in the '80s came when Simmons introduced their SDS-V system in 1980. This was a five-voice (expandable to 7) system with the voices designed individually to produce sounds resembling snare, tom, kick, and percussion sounds. The system came with a "drum kit" made of the now-iconic hexagonal drum pads, of the approximate size and shape of the drums they emulated. Simmons expanded this concept with subsequent models throughout the '80s.
Drum synthesizers fell out of popularity at the end of the '80, in part due to overuse of certain sounds. Roland revived the concept of the dedicated drum synthesizer in the late 1990s with the V-Drums line. However, today there is a lot of crossover between drum machines and drum synthesizers; drum machines such as models from Akai and Korg frequently include an array of finger-played drum pads to allow hand playing, and the V-Drums "brain" units can be sequenced via MIDI. A notable unit is the early 2000's Novation Drumstation, a rackmount synthesizer that does not contain any built-in sequencer capability; it is controlled via MIDI.