If you are curious for technical explanation, there is a rudimentary
introduction to tracking chip at: http://syntaxparty.org/tguide.html
More information to come, but for now have some pictures :-)
The "gAtari" - Atari 2600 with custom tunes playing from assembled code.
The Commodore 64 with tunes playing from an Ultimate 1541 as compiled code
LSDJ for Nintendo Gameboy
Protracker 2.x running on an Amiga 500 (or 1200 in OCS mode)
More Atari 2600 toys!