Elton John played piano on, and performed live in 1974, which number-one John Lennon single?

The John Lennon number-one single featuring Elton John's piano playing and 1974 live performance was “Whatever Gets You thru the Night.” Lennon released it in 1974 as the lead single from his album Walls and Bridges.

Elton John contributed piano, organ, and harmony vocals to the studio recording. He bet Lennon that the song would reach No. 1; Lennon, who was skeptical, promised to join John onstage if it happened. When the single topped the U.S. charts, Lennon fulfilled the agreement at John's Thanksgiving concert at Madison Square Garden on November 28, 1974.

That appearance became Lennon's last major concert performance. The song was his only solo U.S. No. 1 single during his lifetime and topped the Billboard Hot 100, Cashbox, and Record World charts. The live recording with the Elton John Band was later issued on the 1981 EP 28 November 1974 and included in later Lennon and Elton John archival releases. The spelling “thru” is part of the song's canonical title.