Andrey Tarkovsky's 1972 sci-fi masterpiece Solaris is not just a great film about space, it's an all-time great, period. Now, the score to the film is available for free download. And as awesome and spooky sounding as it is, the story of it's creation is arguably better.
You see, the Solaris score was recorded on an ANS synthesizer, which took source audio and etched visible sound waves on glass discs, and then use those same discs to reproduce the sound.
In this case the sine waves generated by the ANS are printed onto five glass discs using a process which Murzin (an optical engineer) had to develop himself. Each disc has 144 individual tracks printed onto it, for a total of 720 microtones (discrete pitches), spanning 10 octaves. This yields a resolution of 1/72 octave (16.67 cents). The modulated light from these wheels is then projected onto the back of the synthesizer's interface. These are arranged in a continuous swath vertically, with low frequencies at the bottom and high frequencies at the top.
The user interface consists of a glass plate covered in non-drying opaque black mastic which constitutes a drawing surface upon which the user makes marks by scratching through the mastic, and therefore allowing light to pass through at that point. In front of the glass plate sits a vertical bank of twenty photocells which send signals to twenty amplifiers and bandpass filters, each with its own gain adjust control. It is akin to a ten-octave equalizer with two knobs per octave. The ANS is fully polyphonic and will generate all 720 pitches simultaneously if required (a vertical scratch would accomplish this).
While actual operation of this thing is pretty tricky to wrap one's head around, the demo in the video shows what the thing looks like and offers a rough idea of how it works. But mostly, it's just further proof that every aspect of the film involved some wonderful, futuristic idea behind it. Now go sit in a dark room and listen to the soundtrack. [Root Strata and Wikipedia via The Daily Swarm]