The incidental music was recorded in December 1964 at Olympic Studios in Barnes with a 30-piece orchestra. The opening and closing theme music are variations on the series' main theme, "The "Thunderbirds" March", and are unique to the episode. Until a very late stage of production, the closing credits were to be accompanied by a sung end theme – "Flying High", performed by Gary Miller – which series composer Barry Gray wrote to contrast with the instrumental opening theme. However, Anderson and Gray later decided that the song was tonally unsuitable and replaced it with the march two weeks before the TV première.