The eerie “whistling sounds” were recorded during the mission’s flight around the dark side of the Moon.

The classic B-movie sci-fi sounds of the eerie, otherworldly theremin were first coined by the great film and television composer Bernard Herrmann, most notably in his 1951 score for the film The Day the Earth Stood Still. Little did Herrmann know how close his orchestration was to actual space music. Transcripts and recordings from the 1969 Apollo 10 lunar mission, recently released by NASA, have revealed that during the astronauts’ journey across the dark side of the moon, a mysterious “whistling space music” was heard through their radio headsets.

It may sound like science fiction, and indeed, the three men who boldly went into lunar orbit that day in 1969 were so baffled by the occurrence they decided not to report it directly to NASA at the time. However after sitting in NASA’s archives for almost 50 years, the recordings of the celestial whistling, heard by astronauts Thomas Stafford, John Young and Eugene Cernan, have now been released to the public for the first time.

The extraordinary tapes have become the subject...