Bohemian Rhapsody turns forty, and Queen marks the anniversary by opening up the studio tapes. Brian May sits at the mixing desk and pulls apart the original multitrack recording layer by layer, isolating Freddie Mercury's vocal stacks and the operatic middle section piece by piece, narrating what each track was built to do. Roger Taylor and studio engineer Justin Shirley Smith join him to walk through the song's construction, from Mercury's original demo to the technical limits of 1970s recording, when performance quirks couldn't be edited out the way they can now, leaving small human imperfections baked into the final mix. Archive footage mixes studio sessions with live performance and the promotional film clip, which the documentary credits as an early forerunner of the music video format later built by MTV. The film also traces the single's commercial life, noting its standing among the biggest-selling British singles ever, ahead of songs by The Beatles and Elton John. Most of the runtime stays inside that mixing desk, with May doing the explaining.