There's this gem of a game on Steam called The Polynomial. I don't really play it for the game part though.
In the most basic sense, it's a space shooter. In another sense, it's a space journey on acid.
You can load up any audio you want in it and the entire thing lights up and moves to the sounds! And it lets you modify so many things, you can get tons of different entrancing effects. I just turn off all enemies, and fly around watching space warp to my tunes.
These screenshots are nice, but nothing compares to seeing it animated! Like I said... space on acid.