Robbo sez, "Bernard Herrmann composed the score for the 1951 film The Day The Earth Stood Still, directed by Robert Wise."
The film itself is a moving icon of the explosion of science fiction culture spawned by the advent of the atomic age. Herrmann pulled out all the stops with this score and in this YouTube posting from LostInTheTime's Channel we get to hear the isolated session tracks when they recorded those portions of the score which used the theremin. I don't know from this recording if it was Paul Shure or Samuel Hoffman performing with the instrument.
I adore Herrmann's film scores, across all genres; he literally changed the entire landscape of modern music through his cinematic works. I also love listening to raw tracks like these – one of the best, of course, is "The Carl Stalling Project", a collection of recordings for the Warner Bros. Looney Tunes cartoons, scored and conducted by Stalling.
And I love the theremin. My son made one from a kit with a cigar box case and we always enjoy cranking it up and scaring the neighbour's cat with our less-than-accurate renditions of Herrmann scores and other SF movie favourites.