the band alone. Plastic Ono Band albums to "Happy Xmas (War Is Over)" (1970–1971) During the summer of 1970, Lennon and Ono undertook primal therapy under the guidance of Arthur Janov in Los Angeles. This therapy had a great effect on Lennon's writing. In the meantime, the Beatles had publicly broken up, and the pair returned to London at the end of September to begin recording on a pair of studio albums, John Lennon/Plastic Ono Band and Yoko Ono/Plastic Ono Band. The core of the Plastic Ono Band backing the two was Klaus Voormann on bass and Ringo Starr on drums. Phil Spector co-produced Lennon's record, and he and Billy Preston played keyboards on some tracks. George Harrison contributed sitar to Ono's album. Lennon's record consisted of straightforward, stripped down rock, while Ono's featured experimental and avant-garde music. Both albums were released on 11 December. The single "Mother" / "Why" was issued, the songs coming from John Lennon and Yoko Ono respectively. In early 1971, Lennon recorded "Power to the People" with a line-up of Billy Preston, Bobby Keys, Klaus Voormann and Alan White. Ono's B-side "Open Your Box" featured Voormann and Jim Gordon. The single was released in March, with the sides credited to "John Lennon/Plastic Ono Band" and "Yoko Ono/Plastic Ono Band" respectively. In the spring and summer of 1971, Lennon and Ono recorded their respective albums Imagine and Fly. Using the same "John Lennon/Plastic Ono Band" and "Yoko Ono/Plastic Ono Band" artist credits, the albums featured contributions from George Harrison, Nicky Hopkins, Klaus Voormann, Alan White, Jim Keltner and Jim Gordon, and Phil Spector co-produced Imagine. On 6 June, Lennon and Ono performed with Frank Zappa and the Mothers of Invention in New York City, later dubbing the collaboration "John & Yoko/Plastic Ono Band with The Mothers of Invention". The next use of the Plastic Ono Band name was the 1971 Christmas single "Happy Xmas (War Is Over)". Credited to "John & Yoko/The Plastic Ono Band", the recording featured drummer Jim Keltner, pianist Nicky Hopkins and guitarists Hugh McCracken, Chris Osbourne (who had played on Fly), Teddy Irwin and Stuart Scharf. The B-side, "Listen, the Snow Is Falling", featured the same musicians as "Happy Xmas", with the addition of Klaus Voormann on bass. Co-produced by Phil Spector, the single was issued on 1 December. Move to New York: Plastic Ono Band with Elephant's Memory (1971–1973) Lennon and