Ring Around the Moon

Filmed February 27th through March 14th, 1974 (fourth episode in production order). Barry Gray took a short leave from the series early on, so he left the soundtrack duties for this episode with Vic Elms (Sylvia Anderson's son-in-law; former guitarist for "Christie" who had the Top 40 hit "Yellow River" in 1970), who had performed the rock parts of the show's opening and closing theme music. Elmes was unable to read or write music, attempting to demonstrate his ideas to the orchestra with his guitar. His lack of professionalism caused most of the players to walk out of the project. Music Editor Alan Willis quickly stepped in and helped get the music recorded, assembling players in a rock format (drums, double bass, organ and piano, and Elmes on guitar), laying out some of Elmes' musical ideas to the players and conducting them himself. Elmes was also unfamiliar with soundtrack work, so several of the tracks were 2-3-minute compositions which Willis later edited to fit the visuals, some of which never made it into the episode. When Gray returned, Elmes was no longer allowed near the studio. Elmes eventually learned the soundtrack art and scored The Ups and Downs of a Handyman (1975), which starred Barry Stokes (Jim Haines on the Voyager's Return (1975) episode) and featured Valerie Leon (the well-endowed Thulian on the Death's Other Dominion (1975) episode). This episode also included one library track; the start of "Drumdramatics No.1" was used when the Alphans on the lunar surface were being threatened by the Sphere.

The episode's biggest plot hole involves the Alphan's mysterious knowledge of the planet Triton's location and sudden demise (Victor even being familiar with the planet's name) which Alpha's computer was unaware of. Koenig claims that Triton was located 2 million light years from their current location. Not only would it be unlikely that they would have any knowledge of a planet that far away, but that distance would place the planet outside the Milky Way galaxy. The episode's novelization by E.C. Tubb solves this by Triton being the moon of Neptune.