Rian Hunter's Super Midi Pak is a SNES cartridge that turns the console—remember those cleanly-sampled but harshly-looping string sections?—into a fully-featured synthesizer.
Inside your SNES is a MIDI synthesizer waiting to be set free… with Super MIDI Pak the wait is over. Play music on your Super Nintendo!
You can pre-order one for $99; the creator invites you to follow him on Twitter if you have questions about this marvelous hack.