In the 1990s Paul McCartney described the song as dominated by Lennon, but written in collaboration, stating: "John mainly sang it so I expect that it was his original idea but we both sat down and wrote it together.

John Lennon, in one of his final interviews, told Playboy magazine that the song was the beginning of a wider audience for Beatles music than the youthful throngs that had fervently followed them from their Liverpool club days.

"It was only after a critic for the [London] Times said we put 'Aeolian cadences' in 'It Won't Be Long' that the middle classes started listening to us.

"[7] Rolling Stone stated that "It Won't Be Long" was "the kind of song Bob Dylan had in mind when he wrote that Beatles chords were 'outrageous, just outrageous.

'"[8] With its composers not being versed in musical theory, the song incorporates chords it "shouldn't", being in the key of E but veering off into D, C and F♯, and "a hybrid of D and Bm".