Tom Richards, who built the machine, has a very short blog here with a couple of bits of extra info on the machine:

http://minioramics.blogspot.co.uk/

Unfortunately, there's not much in the way of info about how the lines on the film map to the synthesizer controls - I found it very odd to watch the film go by, and see busy sections with short discrete notes, sections with long interesting curves, and almost empty sections, but to hear no discernable difference in the audio.