There are two versions of the song. The album version ("Flash's Theme") is in fact the start to the movie, with all the dialogue from the first scene. The single version features dialogue cut from various parts of the movie, most memorably, Brian Blessed's character exclaiming "Gordon's alive?!" This version was also included on the Greatest Hits compilation from 1981.

Flash is sung as a duet between Freddie Mercury and Brian May, with Roger Taylor adding the high harmonies. May plays all of the instruments except for the rhythm section. He used an Imperial Bösendorfer Grand Piano (with 97 keys instead of 88, having an extra octave on the low range), Oberheim OBX synth (which he plays in the video) and his homemade Red Special electric guitar.

On the U.S. charts, "Flash's Theme aka Flash" reached #42 on the Billboard Hot 100. It peaked at #39 on the Cash Box Top 100. It fared much better in Europe, where it was a Top 10 hit in most nations, including #1 in Austria.

The video for the song was filmed at Anvil Studios, London in November 1980 and directed by Don Norman and features the band performing the song to a screen showing clips from the film. An alternate version which was broadcast during the Concert for Kampuchea during 1981 featuring alternate film clips was included on the Flash Gordon 2011 iTunes edition.

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