I love Bernard Herrmann's soundtracks, with "Vertigo" (1958) potentially being my favorite:
Where as Herrmann used no electronic instruments for "Vertigo", he used not only one, but two theremins, plus electric violin, cello, and bass, two Hammond organs, a large studio electric organ, three vibraphones, two glockenspiels, marimba, tam-tam, two bass drums, three sets of timpani, two pianos, celesta, two harps, one horn, three trumpets, three trombones, and four tubas for the soundtrack of "The day the earth stood still" (1951):
(coloured version, original was b/w)
Before "The day the earth stood still"), the Theremin was an acoustic trademark for disturbed mental states, which started with Miklós Rózsa's soundtrack for Hitchcock's "Spellbound" (1945):
And while the title music theme of Herrmann's "The day the earth stood still" from September 1951 might be the most culturally impactful (and most beautiful in my ears), it was not the first sci-fi film using the Theremin to indicate "space" – that was "Rocketship X-M" from 1950 (couldn't find a useful musical snippet on the internetz, sorry) –, it wasn't even the second, that was "The thing from another world" (1951) from April 1951:
It should be noted that in all mentioned films, the theremin has been played by podiatrist Samuel Hoffman.
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