Yesh yesh, some hardware/software combinations that might be of interest to you.
Via c64.sk a while back, I found Musicpad64. It is a BASIC software for C64 by nicovideonico. By controlling it with a Playstation Dance Pad, he’s made this videoclip. It’s a nice song – melancholic and dirty, just the way we like it! We should let our feet do the composing more often.
And via getlofi I discoverred electrokraft who is in the process of making several cartridges for NES to play music with its 2A03. Watch a video clip demonstration of the software in action with his custom built Sonic DrumAxe here. The sounds are not really that interesting, and I am not sure what the software “Super Synth Drums” is capable of. I am guessing that MidiNes is a lot better, but on the other hand you are not programming that straight on the NES.
Gijs Gieskes Hard Soft Synth, surfacing on the web a few months ago, might not be 8-bit (for those of yous that care) but it sounds sort of like it, and it looks great!