In the field of electronic music, a sequencer was originally any device that recorded and played back a sequence of control information for an electronic musical instrument.
Early analog music sequencers used control voltage/trigger interface, but have generally been replaced by digital sequencers utilizing MIDI. A MIDI sequencer plays back MIDI events and MIDI control information at a specified number of beats per minute.
Some synthesizers and almost all music workstations include a built-in MIDI sequencer. There are also standalone hardware MIDI sequencers, such as the Yamaha QY700 .
Software music sequencers run entirely on personal computers. These come in two varieties- pure MIDI sequencers and MIDI/audio sequencers. The former only allows the recording, playing back and editing of MIDI data. The latter adds the ability to sequence MIDI data alongside audio data.
Music sequencing software
Hardware music sequencers
Similarly, music can be sequenced in a sense using trackers such as ModPlug Tracker, and a drum machine can be viewed as a specialized music sequencer.