A sequencer does not make sound itself; it remembers what should happen and when, then tells instruments to play it. Early analogue step sequencers from Moog, ARP and Roland typically offered a row of twelve steps lit one after another, with very little memory. Roland’s MC-8 MicroComposer, announced in 1977, was one of the first digital sequencers, storing about 1,100 notes across eight channels in its original form, and later MIDI sequencers, first in hardware and then in software, brought sequencing into every home studio.
Today the sequencer is usually built into a DAW, a drum machine or a sampler such as the MPC or SP-404. In jazz lo-fi it is where producers decide the amount of swing, the length of each note and how strictly the parts follow the beat.