How Billy Preston Helped the Beatles Play Nice on 'Get Back'
When George Harrison, who had briefly quit the Beatles in early 1969, decided to return to the band, he brought with him a secret weapon: keyboardist Billy Preston.
Harrison’s departure was the result of infighting and strained tensions within the Beatles. The bandmates were infamously at each other’s throats by this point, with starkly differing viewpoints on how the band was to proceed.
During his break from the group, Harrison caught a performance by Ray Charles in London. On the stage that night was Preston, whom Harrison and his fellow Beatles had befriended during their years in Hamburg. Excited to see his old pal, Harrison sent Preston a message inviting him to join the Beatles in the studio.
This wasn’t the first time a non-Beatle had joined the Fabs' ranks. Harrison had used the same method during the contentious White Album sessions, having Eric Clapton join the group for “White My Guitar Gently Weeps.”
Source: ultimateclassicrock.com