Oskar Fischinger was a pioneering animator who created abstract films that worked in tandem with the music he chose to illustrate. Shying away from anything representational, he used color, shape and motion to visually sympathize with the music heard on the soundtrack. His work began in the 20s (!) and carried through the early 60s.

Jordan Belson was another abstract film artist, working through edits of film made with optics in realtime, rather than anything animated. His incredible, hypnotic, mandala-fused films are not to be missed. His early work segued into the San Francisco Vortex Concerts which began in the late 50s. We lost Belson just a few weeks ago to cancer at the age of 85.
I didn’t hear the term Visual Music before the internet, but these two are the urtext for me. Did I just use the word urtext? Wow. Anyways: For me, these two are the original – the yardstick by which I’ll always measure any other. Watching any one of these pieces can push the mind into new musical territory: you’ll hear a rhythm, see a rhythm, and the mind will begin to introduce a third rhythm. Odd, involuntary participation. I saw Black Dice a few years back and their visuals pushed in a similar direction.
The Center for Visual Music is trusted custodian to the estate of each of these filmmakers. They’ve put out brilliant DVD’s of each artist’s work, and I can’t say enough good things about the quality bar. They have, however, taken all youtube videos down in the process. :/ I found one here, though! At any rate, check the DVDs out and by them – you will NOT be disappointed.
I must give a shout out to the Northwest Film Forum and Spencer Sundell, who have brought this type of work (a few times, programmed with CVM) to Seattle many times in the past few years. You guys are awesome!