Prophet-5

Before 1978 a synth sound was a set of knob positions, and getting it back meant drawing the front panel on paper. Dave Smith at Sequential Circuits had a Z80 read and set every parameter, so dozens of sounds could be stored and recalled at the press of a button. Five voices, each with two oscillators, a filter and envelopes, made it genuinely polyphonic rather than polyphonic on the spec sheet.

Early units were infamous for drifting out of tune as they warmed up; later revisions switched to Curtis chips and settled down. It was on everything in the early 1980s, and in 2020 a newly manufactured version appeared with essentially the same architecture, which says something about how right it was the first time.