John Lennon and Yoko Ono performed with Frank Zappa and The Mothers of Invention on 6 June 1971.
Earlier in the day, Lennon and Ono had been introduced to Zappa at the Mayfair Hotel. He was doing an interview with radio reporter Howard Smith, who had been acting as Lennon and Ono’s New York guide since their arrival. Zappa invited them into his hotel room, and asked Lennon and Ono to jam with The Mothers of Invention that night at the Fillmore East.
After leaving the hotel, Lennon and Ono watched David Peel perform with The Lower East Side at Washington Square Park, then Smith took them to the WPLJ studios, where he interviewed them and allowed them free rein on the air.
That evening Lennon and Ono joined The Mothers of Invention backstage at the Fillmore East, during the show’s encore. They performed four songs: a cover of The Olympics’ ‘Well (Baby Please Don’t Go)’, followed by the largely-improvised ‘Jamrag’, ‘Scumbag’, and ‘Aü’ (‘Jamrag’ was actually an uncredited Zappa song, ‘King Kong’, from his 1969 album Uncle Meat).
I thought he [Lennon] had a pretty good sense of humour, so I invited him to come down and jam with us at the Fillmore East. We had already book in a recording truck because we were making the Live At The Fillmore album at the time. After they had sat in with us, an arrangement was made that we would both have access to the tapes. He wanted to release it with his mix and I had the right to release it with my mix – so that’s how that one section came out.
The recordings were released in 1972 on the album Some Time In New York City.