The Beatles were an English rock band formed in Liverpool in 1960 and one of the most commercially successful and critically acclaimed acts in the history of popular music. The group's best-known lineup consisted of John Lennon (rhythm guitar, vocals), Paul McCartney (bass guitar, vocals), George Harrison (lead guitar, vocals) and Ringo Starr (drums, vocals). Rooted in skiffle and 1950s rock and roll, the group later worked in many genres ranging from pop ballads to psychedelic rock, often incorporating classical and other elements in innovative ways. Their enormous popularity first emerged as "Beatlemania"; as their songwriting grew in sophistication, by the late 1960s they came to be perceived by many fans and cultural observers as an embodiment of the ideals shared by the era's sociocultural revolutions. As a five-piece line-up of Lennon, McCartney and Harrison on guitar and vocals, with Stuart Sutcliffe (bass) and Pete Best (drums), the band built their reputation playing clubs in Liverpool and Hamburg over a three-year period from 1960. Sutcliffe left the group in 1961, and Best was replaced by Starr the following year.