Earlier analog music sequencers previously existed using the control voltage / trigger interface, but have now been replaced by digital sequencers for all practical purposes. A MIDI sequencer plays back MIDI events and MIDI control information at a specified number of beats per minute.
Many synth modules, such as the Korg Triton rack module, include a MIDI sequencer built into their design. There are also standalone MIDI sequencers, such as the Yamaha QY-70. However, most modern sequencers consist of a software package running on a personal computer.