Texas Instruments SN76477N

https://en.wikipedia.org/wiki/Texas_Instruments_SN76477

http://www.righto.com/2018/05/inside-76477-space-invaders-sound.html

http://www.righto.com/2017/04/reverse-engineering-76477-space.html

PD pd-0.50-2

https://en.wikipedia.org/wiki/Pure_Data

Pure Data (Pd) is a visual programming language developed by Miller Puckette in the 1990s for creating interactive computer music and multimedia works. While Puckette is the main author of the program, Pd is an open-source project with a large developer base working on new extensions. It is released under a license similar to the BSD license.

friends

https://electric.kitchen

Midi

https://ccrma.stanford.edu/~craig/articles/linuxmidi/misc/essenmidi.html