Story 
"Strawberry Fields Forever" is a song by the English rock band the Beatles, written by John Lennon and credited to Lennon–McCartney. It was released on 13 February 1967 as a double A-side single with "Penny Lane". It represented a departure from the group's previous singles and a novel listening experience for the contemporary pop audience. [Wikipedia]
Lennon wrote it in Almería, Spain, while filming Dick Lester's How I Won the War in autumn 1966. Strawberry Field was the name of a Salvation Army children's home in Woolton, near Lennon's Aunt Mimi's house, where he had played as a child. The lyric is among the most explicitly autobiographical and Lennon-vulnerable of his career. George Martin left to his own creative devices during sessions, composing the distinctive cello line moving in counterpoint to the melody while Lennon was uncertain (Kozinn 1995, p.16).
Two completely separate takes, recorded in different keys and at different tempos, were spliced together by George Martin and Geoff Emerick on Lennon's instruction (he liked the beginning of one and the end of the other). The slower take was sped up; the faster one slowed down — and by chance the two converged in approximately the same key. The splice point is at roughly the one-minute mark. Mellotron, slide cellos, brass, backwards drums and Indian percussion swarm across the four-track. Final mixing was completed only days before its 17 February 1967 release as a double A-side single with Penny Lane. The splice between two recordings in different keys and tempos was executed at a shallow angle to resemble a crossfade rather than an abrupt cut, requiring hours of meticulous work by Martin and Emerick (Emerick 2006, Strawberry Fields Forever chapter). The composition reflected Lennon's childhood nostalgia and introspective impulse; the elaborate studio arrangement by Martin, initially rejected by Lennon, eventually became iconic through creative splicing (MacDonald 1994, p.103).