A self-taught musician, McCartney is proficient on bass, guitar, keyboards, and drums. He is known for his melodic approach to bass-playing (mainly playing with a plectrum), his versatile and wide tenor vocal range (spanning over four octaves), and his eclecticism (exploring styles ranging from early 20th-century pop to classical and electronica). McCartney began his career as a member of the Quarrymen in 1957, which evolved into the Beatles in 1960. Starting in 1967, he gradually became the Beatles' de facto leader and business manager, providing the creative impetus for their records after Sgt. Pepper's Lonely Hearts Club Band. Of his Beatles songs, more than 2,200 artists have covered "Yesterday" (1965), making it one of the most covered songs in popular music history.