There's a fellow out there who wrote a program called The Music Animation Machine.  This piece of software plays MIDI files with animated graphics (akin to visualizers in other programs).  What make this worthy of a TMK post is that some lovely folks in Japan used this program to make an graphical Mario MIDI.

Interesting, don't you think?

More information, and a few other game MIDI videos, are available on his MAM MIDI Player on Nico Nico Douga page (Nico Nico Douga being a Japanese video and commentary site).

Go take a look!  http://www.youtube.com/watch?v=-wkI7hg65F0