Back before I really knew what MIDI was, I was running a really old keyboard on a 486. It was this product: http://www.oldsoftware.com/MusicStar.html
Years later I dug up this thing from storage and hooked it up to the MIDI port on a Korg MS2000R synthesizer (rackmount version of the MS2000, so no built in keyboard) and it was pretty fun. Many modern basic consumer keyboards you find at places like Radioshack also use MIDI input/output, as I picked up a larger Yamaha keyboard to use on the synthesizer instead of the smaller MusicStar keyboard. Also added a Korg Electribe ER-1 beat machine into the mix and it was crazy what you could do with all of it. For modern computer use, you can pretty much get all of these and the older synths as VST plugins for use with software like Cubase. I think I have some older 68K MIDI software on my server but most of that stuff is before my time.
Years later I dug up this thing from storage and hooked it up to the MIDI port on a Korg MS2000R synthesizer (rackmount version of the MS2000, so no built in keyboard) and it was pretty fun. Many modern basic consumer keyboards you find at places like Radioshack also use MIDI input/output, as I picked up a larger Yamaha keyboard to use on the synthesizer instead of the smaller MusicStar keyboard. Also added a Korg Electribe ER-1 beat machine into the mix and it was crazy what you could do with all of it. For modern computer use, you can pretty much get all of these and the older synths as VST plugins for use with software like Cubase. I think I have some older 68K MIDI software on my server but most of that stuff is before my time.