I'll just throw some more ES5503 DOC love here. It's also the audio chip in the Apple IIGS. In 1986, having a stock home computer playing 32 simultaneous hardware voices (without software mixing), each with hardware pan ... was remarkable. Otherwise you were stuck with 3 or maybe 4 hardware voices. e.g. the timbre and filter of the C64 SID chip was gorgeous (another Bob Yannes design), but 3 voices was all you got. And just 3 square waves and noise on the Ataris of the era. Chords or complex harmony? Fire up the arpeggiators! Lol.

When I browse the demoscene I'm always a bit surprised there's not much Apple IIGS content. Graphically, it was stunted, but the ES5503 DOC was a pro synth engine right there next to the 6502 ... yowza.