There was a music program for the Sol-20 microcomputer, which was an 8080 running a tad slower than 2MHz. 4 voice polyphony. The program came with a tiny card

There was a music program for the Sol-20 microcomputer, which was an 8080 running a tad slower than 2MHz. 4 voice polyphony. The program came with a tiny card plugged into the S-100 bus consisting of nothing more than an RC filter. The Sol didn't use interrupts. The program worked by toggling EI/DI (enable and disable interrupt) to cause one of the pins on the s-100 bus to toggle. The intonation of especially suffers because those notes are more affected by the fixed 8080 clock cycle. Here is a clip of it. This clip is from an emulator of the Sol-20, and it uses a higher order filter than the first order RC used by the original hardware. The real hardware is harsher sounding than this. The ten seconds of the 25 second clip is unimpressive, but the 2nd half shows how much can be done with such limited hardware. http://sol20.org/media/d-minor.mp3 http://sol20.org/media/d-minor.mp3