The Commodore VIC-20 was an 8-bit home computer first released in 1980.  The "Video Interface Chip" (MOS Technology 6560/6561) was responsible for both the audio and visual graphics of the machine.  On the audio side, the VIC chip had 3 square wave channels and 1 white noise channel and a global volume control.  Each square wave had a range of 3 octaves, but were tuned an octave apart from each other.  This gives the chip a five octave range total.

'[b] How to make VIC-20 music'[/b] 

'[l[http://battleofthebits.com/academy/GroupThread/7606/mod2vic+-+VIC-20+tunes+for+the+masses/[mod2vic]
Compose your music in any Fasttracker compatible editor, then convert it to .prg with this Python-based utility by cce.

'[l[http://www.kahlin.net/daniel/victracker/[VIC-Tracker 2.0]
The classic way of doing things. A real tracker running on real hardware (or in an emulator), made by Daniel Kahlin. Slightly unnerving because it does not use note names.

'[l[http://home.eunet.no/~ggallefo/tools/vdi1.zip[VIC Duzz It]
Another tracker that runs on the actual machine, made by Glenn Rune Gallefoss. More complicated than VIC-Tracker, but also more advanced. Unlike VIC-Tracker, it requires full memory expansion.