I really want to know more about this chip especially about the sound engine. if you read about the chip on wikipedia it will tell you that it is a 4 voice machine with 3 square waves and 1 noise channel. it sounds pretty basic but if you actually listen to audio made by the machine it has a lot of quirks and a unique sound. in particular the noise channel most obviously sounds really weird. I have been trying to figure out how the noise generation is created by the chip.
it almost sounds like the noise is made with a filter thrown over it with a high resonance setting. i doubt very much that its wave is true noise or even pseudo noise.
http://en.wikipedia.org/wiki/MOS_Technology_VIC
if you dont know what the hell i am talking about take a listen to the sample below:
http://www.armagon.org/mods/warlord/201
IC-20).mp3
the song is made by warlord. he has one of the few full vic-20 releases that i have found available called VICious cycle.