Jupiter Ace 1-bit music engines. ( proof-of-concept ) All credit to Shiru and Utz.
Original engines for ZX Spectrum by Shiru & Utz. Utz modified engines to run on ZX81; and these have in turn been assembled to run on the Jupiter Ace as proof-of-concept.
Assembled to $4000. Using emulator EightyOne, load .BIN file in as a memory block, back in the Forth prompt, type "16384 CALL" to make things go. For real hardware, a tape header would need to be added, and a .WAV file created.