The Synthanola punch-tape sequencer & synthesizer – an entry in the 555 contest – does its own version of Bach’s Inventions # 8 & 13.
The Synthanola is a three channel music synthesizer, not so well-tempered, capable of four octaves per chanel.
555’s are used to generate each octave for each voice (or channel). There are twelve 555 timer IC’s used for the synthesizer section and two more for tempo control and paper speed. It is sequenced by a Heathkit H-10 paper tape unit and programmed with a 486 PC running QBasic.
Details at retroarchive.