I think you're thinking of the sounds of the fabled Atari 2600 or the Commodore 64.
There's plenty of sample libraries available with those sounds, to use in your software sample playback device.
There's some free virtual synths out there too:
http://www.synthtopia.com/content/20...ari-synth-vst/
only for Windows, though (bah!)
You'll need a lot more than bit reduction and distortion, etc. to get a bass guitar to make those sounds if that's what you're after. Darn near impossible (unless you're triggering samples, then you could use any trigger device). Not to say you won't land on something ELSE cool trying though
