Hurwitz noted the tension in the song between the aspirations of the singers and the uncertain outcome of their efforts, noting "It’s an optimistic song, but it’s also about unfulfilled dreams." Paul said, "You pursue that dream, and you go to bed and get up the next day, and it’s a gorgeous day. It encourages you in one breath, and in another breath doesn’t acknowledge that you just failed miserably. You wake up and it doesn’t match your mood. It’s a bright and shiny day." The song is written in the key of E major, with a tempo of 126 beats per minute. It generally follows an A–B–Cm–Gm chord progression, and has a vocal range for the various parts of G3–C5. Hurwitz composed the song with a fast-paced tempo predominantly using major keys, but often using minor keys as well, making it "more bittersweet than it may seem on its face" according to Hurwitz. The song also has densely layered background vocals and a full 95-piece orchestra and 40-person choir. Hurwitz tried to feature different elements of the orchestration as the visuals followed different members of the ensemble.
Shooting and choreography
The sequence - the first of the film to be shot - was filmed over two days in August 2015. The song was filmed on a 130-foot-high express ramp of the Judge Harry Pregerson Interchange between the Harbor Freeway and the Glenn Anderson Freeway in South Los Angeles. The ramp was closed for the two full days of filming. The rest of the highway was left open, so that normal traffic is visible in the background. The sequence was initially planned to be on a ground-level ramp, but it was changed to the interchange to give a sense of the vastness of the city. Director Damien Chazelle also likened the number's location on a highway to the Yellow Brick Road in The Wizard of Oz. The number was shot in three takes, which were edited to give the appearance of a single six-minute long take. Moore spent between three and four months preparing for the shoot, which involved over 60 cars, 30 dancers, and 100 extras. The number was choreographed with a single dancer at its beginning, with other dancers joining in incrementally, to avoid having everyone abruptly start dancing at once. The ensemble also included several stunt performers. Initial rehearsals with ten dancers occurred in a studio parking lot using about 20 staff members' cars. The number was initially planned to be preceded by an overture, but during editing it was found that this slowed the opening too much. Film editorTom Cross noted that Chazelle "realized that for people to accept that it's a musical, you have to announce it confidently at the beginning," and that displaying the film's title on the final beat of the song caused to serve as an overture itself. On screen, dancer Reshma Gajjar appears to sing the opening lines, but the lead female vocals were actually provided by vocalist Angela Parrish, who never appears in the film. The filmmakers had hoped to find a woman "who could both sing and dance on camera" to launch the opening number, but ended up finding their dancer first and then had to conduct separate auditions for a vocalist during post-production in the spring of 2016.
