When I made the film The Flicker in 1965-66 my principal motivation was to explore the possibilities for harmonic expression using a sensory mode other than sound. The experience of "flicker" - its peculiar entrapment of the central nervous system, by ocular driving - occurs over a frequency range of about 4 to 40 flashes per second (fps). I used film (at 24 fps) as a sort of "tonic," and devised patterns of frames which would represent combinations of frequencies - heterodyned, or rather multiplexed together. I was interested to see whether there might be combination-frequency effects that would occur with flicker, analogous to the combination-tone effects that are responsible for consonance in musical sound.
That was a sophisticated idea. Even though the frequency range of flicker is theoretically large enough - though barely - for harmonic modulation products to occur, The Flicker did not convincingly demonstrate the existence of any harmonic flicker structures. Nevertheless, the hypnotic phenomena and trance states that characterize flicker drew my attention again later, when I was working in the 70s and 80s on mind-altering, on attentional states, and on Music and the Mind of the World.