The Roland MC-4 MicroComposer is a vintage analog sequencer from the early 1980s. It was used by many electronic musicians of the time, including Jean-Michel Jarre, Tangerine Dream, and Kraftwerk. The MC-4 is a step sequencer, meaning it allows users to program a sequence of notes and rhythms by entering them one step at a time. It has a maximum of 256 steps, and can store up to 16 different sequences. It also has a built-in arpeggiator and a variety of sound-shaping features. The MC-4 is still sought after by vintage synth enthusiasts and is still used in some modern music production.