Pink Floyd were an English rock band formed in London in 1965 by students Syd Barrett on guitar and lead vocals, Nick Mason on drums, Roger Waters on bass and vocals, and Richard Wright on keyboards and vocals. Guitarist David Gilmour joined in December 1967, with Barrett leaving soon after due to health issues. The group achieved worldwide acclaim, initially with innovative psychedelic music, and later in a genre that came to be termed progressive rock. Distinguished by philosophical lyrics, musical experimentation, frequent use of sound effects and elaborate live shows, Pink Floyd remains one of the most commercially successful and influential groups in the history of popular music. Pink Floyd were inducted into the US Rock and Roll Hall of Fame in 1996, and the UK Music Hall of Fame in 2005. By 2013, the band had sold more than 250 million records worldwide, including 75 million certified units in the United States.