Most of The Beatles’ ninth album, released in 1968, was composed while John Lennon, Paul McCartney, George Harrison and Ringo Starr were on a transcendental meditation course with Maharishi Mahesh Yogi in India. Although it received mixed reviews on its release, The Beatles is now seen as one of the greatest albums of all time. With contributions by all four Beatles, it is a wildly eclectic collection of songs that play with a variety of musical genres, including the proto-metal “Helter Skelter” and the Yoko Ono-influenced avant-garde experiment “Revolution 9”.