In the "" documentary, Wilson described the song as "what children everywhere go through ... wouldn't it be nice if we were older, or could run away and get married". Wilson added in 1996, "'Wouldn't It Be Nice' was not a real long song, but it's a very 'up' song. It expresses the frustrations of youth, what you can't have, what you really want and you have to wait for it." The song expresses "the need to have the freedom to live with somebody," according to Brian. "The idea is, the more we talk about it, the more we want it, but let's talk about it anyway. Let's talk it over, let's talk about what we might have if we really got down to it." Asher has said that Wilson was "constantly looking for topics that kids could relate to. Even though he was dealing in the most advanced score-charts and arrangements, he was still incredibly conscious of this commercial thing. This absolute need to relate." Music journalist Nick Kent responds:  "Wouldn't It Be Nice" begins with an eight-beat introduction in the key of A major. Following a single drum hit, the song shifts to the remote flat submediant key of F. Classical composer John Adams called this key change "nothing new in the classical or jazz world, but appearing here in the context of a standard rock-and-roll song, it felt novel and fresh. More than any other songwriter of that era, Brian Wilson understood the value of harmonic surprise." The verse bass line was inspired by the Ronettes' "Be My Baby" (1963). The bridge section features players in different keys. Bassist Lyle Ritz, who was playing in D major, mistook the arrangement as an error, as he explains: "[The] rest of the band was in another key. I knew that was wrong. So during a break, I looked at everybody else's music to see if it was a mistake. Because you can't do that. But he [Brian] pulled it off." The song uses a ritardando before its bridge, a device that doesn't often appear in pop music, but does in classical music. When the bridge is entered, the song modulates down a minor third from F to D major; this same key change from F to D also occurs in "Let's Go Away for Awhile", another Wilson composition from "Pet Sounds". The instrumental track was recorded at Gold Star Studios on January 22, 1966.