New strains developed between the band members regarding the appointment of a financial adviser, the need for which had become evident without Epstein to manage business affairs. Lennon, Harrison and Starr favoured Allen Klein, who had managed the Rolling Stones and Sam Cooke; McCartney wanted Lee and John Eastman – father and brother, respectively, of Linda Eastman, whom McCartney married on 12 March. Agreement could not be reached, so both Klein and the Eastmans were temporarily appointed: Klein as the Beatles' business manager and the Eastmans as their lawyers. Further conflict ensued, however, and financial opportunities were lost. On 8 May, Klein was named sole manager of the band, the Eastmans having previously been dismissed as the Beatles' lawyers. McCartney refused to sign the management contract with Klein, but he was out-voted by the other Beatles.Martin stated that he was surprised when McCartney asked him to produce another album, as the Get Back sessions had been "a miserable experience" and he had "thought it was the end of the road for all of us". The primary recording sessions for Abbey Road began on 2 July 1969. Lennon, who rejected Martin's proposed format of a "continuously moving piece of music", wanted his and McCartney's songs to occupy separate sides of the album. The eventual format, with individually composed songs on the first side and the second consisting largely of a medley, was McCartney's suggested compromise. On 4 July, the first solo single by a Beatle was released: Lennon's "Give Peace a Chance", credited to the Plastic Ono Band. The completion and mixing of "I Want You (She's So Heavy)" on 20 August 1969 was the last occasion on which all four Beatles were together in the same studio. Lennon announced his departure to the rest of the group on 20 September, but agreed to withhold a public announcement to avoid undermining sales of the forthcoming album.Released six days after Lennon's declaration, Abbey Road sold 4 million copies within three months and topped the UK charts for a total of seventeen weeks. Its second track, the ballad "Something", was issued as a single – the only Harrison composition ever to appear as a Beatles A-side. Abbey Road received mixed reviews, although the medley met with general acclaim. Unterberger considers it "a fitting swan song for the group", containing "some of the greatest harmonies to be heard on any rock record". Musicologist and author Ian MacDonald calls the album "erratic and often hollow", despite the "semblance of unity and coherence" offered by the medley. Martin has singled it out as his personal favourite of all the band's albums; Lennon said it was "competent" but had "no life in it". Recording engineer Emerick notes that the replacement of the studio's valve mixing console with a transistorised one yielded a less punchy sound, leaving the group frustrated at the thinner tone and lack of impact and contributing to its "kinder, gentler" feel relative to their previous albums.For the still unfinished Get Back album, one last song, Harrison's "I Me Mine", was recorded on 3 January 1970. Lennon, in Denmark at the time, did not participate. In March, rejecting the work Johns had done on the project, now retitled Let It Be, Klein gave the session tapes to American producer Phil Spector, who had recently produced Lennon's solo single "Instant Karma!" In addition to remixing the material, Spector edited, spliced and overdubbed several of the recordings that had been intended as "live". McCartney was unhappy with the producer's approach and particularly dissatisfied with the lavish orchestration on "The Long and Winding Road", which involved a fourteen-voice choir and 36-piece instrumental ensemble. McCartney's demands that the alterations to the song be reverted were ignored, and he publicly announced his departure from the band on 10 April 1970, a week before the release of his first, self-titled solo album.On 8 May, the Spector-produced Let It Be was released. Its accompanying single, "The Long and Winding Road", was the Beatles' last; it was released in the United States, but not in the UK. The Let It Be documentary film followed later that month, and would win the 1970 Academy Award for Best Original Song Score. Sunday Telegraph critic Penelope Gilliatt called it "a very bad film and a touching one ... about the breaking apart of this reassuring, geometrically perfect, once apparently ageless family of siblings". Several reviewers stated that some of the performances in the film sounded better than their analogous album tracks. Describing Let It Be as the "only Beatles album to occasion negative, even hostile reviews", Unterberger calls it "on the whole underrated"; he singles out "some good moments of straight hard rock in 'I've Got a Feeling' and 'Dig a Pony'", and praises "Let It Be", "Get Back", and "the folky 'Two of Us', with John and Paul harmonising together". McCartney filed suit for the dissolution of the Beatles' contractual partnership on 31 December 1970. Legal disputes continued long after their break-up, and the dissolution was not formalised until 29 December 1974, when John Lennon signed the paperwork terminating the partnership while on vacation with his family at Walt Disney World Resort in Florida.

Question: What is the last name of the Beatle who released the first solo single?
Answer: Lennon