Reading Albert Glinsky's book on inventor Leon Theremin, I saw mention of a filmmaker I'd never heard of, Mary Ellen Bute. I found a couple of her works posted on YouTube by AnimArchiv.
Rhythm In Light:
Looking around for Bute, I came across John Whitney's computer graphics work, Arabesque (courtesy postingoldtapes):
And some work of Harry Smith (courtesy donjuanauxenfers):
For those of you wondering: yep, it's the same Harry Smith who helped kickstart the folk music revival in the mid 20th century with his LP compilation of old 78s, Anthology of American Folk Music.