To give the appearance of seamlessness to the space ship, the crack around the door was filled with putty, then painted over. When the door opened the putty was torn apart, making the door seem to simply appear.
The Day The Earth Stood Still: Original Motion Picture Soundtrack
Bernard Herrmann - Prelude/Outer Space/Radar (The Day The Earth Stood Still: Original Motion Picture Soundtrack)
“[Herrmann’s score for the sci-fi classic The Day The Earth Stood Still] was another scoring milestone that anticipated the era of electronic music with its then unheard of instrumentation for electric violin, electric bass, two high and low electric theremins, four pianos, four harps and a ‘very strange section of about 30-odd brass.’…What the film needed was an extraterrestrial strangeness, a sense of the bizarre and unsettling; this Herrmann achieved through his wisely sparse electronic soundtrack.
If the music’s impact is lessened today, the reason is not the score itself but the host of inferior imitations its success spawned.”
-excerpted from A Heart at Fire’s Center: The Life and Music of Bernard Herrmann by Steven Smith