At the moment when Paul McCartney joined John Lennon and they started recording with the Beatles, McCartney’s skill with various instruments was a big differentiator (and it still is during the musician’s solo shows). This highlight led McCartney to record tracks like the classic “Yesterday”, with no other Beatle on the record.
Because in addition to bass, piano, guitar and voice, McCartney also knew how to play the drums enough to apply for the job. In “The Ballad of John and Yoko”, the last Beatles song to top the UK charts, McCartney leads the drums.
Paul McCartney on the drums of “The Ballad of John and Yoko”
After having married Yoko Ono, John Lennon wrote a song about the adventures he lived with the artist. And that resulted in “The Ballad of John and Yoko”. When released, the track received full press attention.
When the couple returned to London, Lennon wanted to vent and decided to record a new song. The problem was that Ringo and George Harrison were out of town in April 1969. Without a second thought, Lennon contacted McCartney so they could finish the song.
With Lennon on guitar and McCartney on the other instruments (including bass, piano and drums), they ended the recording at 9 pm. When considering that the band could spend a week to finish the song, that seemed like something efficient. And Lennon would not have achieved any of this without McCartney.