The above video is by Stephen Malinowski, a musician and computer programmer who has been attempting to visualize complex musical scores. Watch it full screen for the best effect.
Here is an NPR interview with Malinowski, where he talks about his process.
"People usually respond to sound in a unitary way. It's the reason why you can't follow more than one conversation at a time at a party, for example. But with vision, your brain is trained to comprehend multiple things at once: you can take in many more elements simultaneously. In music, there's often much more going on than you can grasp in that moment of hearing. When you have a visualization, your eyes lead your ears through the music. You take advantage of your brain's ability to process multiple pieces of visual information simultaneously."