McLaren, founding animator of the National Film Board of Canada’s animation studio, treated the filmstrip as an instrument: painting and scratching images frame by frame, and in works like Dots and Synchromy drawing the soundtrack too, striping the optical audio area by hand so the picture literally is the sound.
Synchromy (1971) makes the fusion explicit: the patterns on screen are the very shapes generating the tones heard.
His work is the limit case of audio-visual correspondence, zero mapping ambiguity, one artifact producing both channels, and a touchstone for anyone designing how sound and image should bind.