Studio style evolution
Many observers have said that understanding the success of The Beatles and their music begins with an appreciation for the ways in which they (especially Lennon and McCartney) blended their voices as instruments.
The role of producer George Martin is often cited as a crucial element in their success. He used his experience to bring out the potential in the group, recognising and nurturing their creativity rather than imposing his views.
Their demands to create new sounds with every recording, personal experiments with psychedelic drugs and the studio expertise of EMI staff engineers including Norman Smith, Ken Townshend and Geoff Emerick all played significant parts in the innovative qualities of the albums Rubber Soul (1965), Revolver (1966) and Sgt. Pepper's Lonely Hearts Club Band (1967).
While most recording artists of the time were satisfied with using two, three or four tracks in the studio, The Beatles began to use linked pairs of four-track decks, and ping-ponging tracks two and three times became common. (EMI delayed the introduction of eight-track recording, already becoming common in American studios, until 1968 at Abbey Road.) Along with studio tricks such as sound effects, unconventional microphone placements, automatic double tracking and vari-speed recording, The Beatles began augmenting their recordings using instruments considered unconventional for pop music at the time, including string and brass ensembles, Indian instruments such as the sitar and the swarmandel, tape loops and early electronic instruments, including John Lennon's Mellotron.
The group gradually took greater charge of their own productions and McCartney's growing dominance in this role, especially after the death of Epstein, played a part in the eventual split of the group. Internal divisions within the band had been a small but growing problem during their earlier career; most notably, this was reflected in the difficulty that George Harrison experienced in getting his own songs onto Beatles' albums, and in the growing artistic and personal estrangement between Lennon and McCartney.
Drug use, personal factors and, above all, the unrelenting pressures and demands of their worldwide fame inevitably intensified these stresses. By the time of the sessions for The Beatles (The White Album), released in November 1968, the once close-knit members were clearly drifting apart both musically and personally. Several tracks were cut as de facto solo recordings by the principal composer, with the other band members more or less relegated to the role of session musician. This isolation is probably most notable on Revolution 9, a wildly experimental John Lennon/Yoko Ono concoction of tape loops, "found sounds," and other studio trickery that the other Beatles reportedly despised and tried to keep off the album. However, it was McCartney who had the strongest interest in the music of Karlheinz Stockhausen, whose Hymnen was heavily influential on Revolution 9. Early Beatles use of "tape loops" on Tomorrow Never Knows were assembled primarily by McCartney.
Harrison's While My Guitar Gently Weeps even featured an outside musician (his friend Eric Clapton) performing the guitar solo; Clapton was reportedly brought in as the result of a bitter dispute between Harrison and Lennon that drove Starr to take a two-week hiatus. During this time McCartney played drums on some of the tracks on the album, including Back in the USSR, on which he also overdubbed most of the lead guitar parts. McCartney had played lead guitar solos on selected songs as far as 1966's Taxman (ironically, a Harrison composition).
The rapidly deteriorating relationships marred the troubled Get Back sessions in January 1969 — Lennon later denounced them as being the worst recordings of their career — and the project was made even more stressful by the presence of a film crew hired to capture the proceedings for a planned movie (which eventually became the Let It Be documentary).
By this time another very significant factor had emerged — Lennon's passionate affair with Japanese artist Yoko Ono. The couple quickly became inseparable and Lennon further alienated the other Beatles by bringing Ono to almost every recording session, breaking the band's long-standing rule against outsiders at sessions. Ono came to be singled out as "the woman who broke up The Beatles" - although after Lennon's death, the surviving three Beatles denied Ono's presence had been a major influence in the breakup.
However, the band's differences were more or less put aside later in the year for the recording of what became their valedictory album, Abbey Road, which the group later recalled as being among the most enjoyable of their career.
While "The White Album" and the original "Get Back" sessions emphasised a return to basic pop-rock song structures, Abbey Road took a step back in the direction of glossy production, although this time primarily consisting of instrumental backing produced by the classically-trained George Martin to help mold together disparate song fragments into a unified, orchestral suite in the tradition of classical compositions.
Abbey Road featured considerable use of synthesisers, but usually in more conventional musical contexts rather than as a source for bizarre and unusual sound effects.
By the end of 1969 both Lennon and McCartney had effectively left the band and the only piece of unfinished business was the as-yet unreleased "Get Back" project. The Beatles had been very unhappy with the original tapes from the "Get Back" sessions (produced as usual by George Martin), and for some time it looked as if the material would be scrapped altogether. After a delay of several months, American producer Phil Spector was brought in to edit, remix and overdub the tapes, and his heavily-orchestrated "Wall of Sound" production characterised the eventual release of the Let It Be album, released in early 1970 nearly a year after the group had ceased to function on an active basis.
By this time, Lennon and Harrison had effectively decided to leave the band. McCartney made the move official at the start of 1970 when he began legal proceedings to dissolve the band's business partnership.
Each Beatle went on to a successful solo career.