GWave:
https://youtu.be/ZRDdKZ7V54I?t=1247
>"Three different tables are required to output sound:
1) Wave Table
2) Sound Vector Table (Synth Presets)
3) Frequency Pattern Table"
The Walsh Function sound machine:
https://youtu.be/ZRDdKZ7V54I?t=1449
Related:
Microcomputer-Controlled Sound Processing Using Walsh Functions, Maurice Rozenberg, 1979:
https://www.jstor.org/stable/3679755