The discography of the English rock group Pink Floyd consists of 15 studio albums, four live albums, 12 compilation albums, five box sets, three extended plays, and 27 singles. Formed in 1965, Pink Floyd initially earned recognition for their psychedelic or space rock music, and, as they evolved, for their progressive rock music. The group have sold over 250 million records worldwide, including 75 million units sold in the United States. Pink Floyd first achieved success in London's underground music scene, when they were led by singer and guitarist Syd Barrett. The group signed a management deal with Peter Jenner and Andrew King (Blackhill Enterprises) in October 1966, and recorded a demo shortly afterwards to attract record label interest. They subsequently signed with EMI Columbia and released their first single, "Arnold Layne" on 11 March 1967, followed by the album The Piper at the Gates of Dawn in August. Barrett's erratic behaviour led to singer and guitarist David Gilmour joining the group; both appear on the second album, A Saucerful of Secrets. Barrett officially left on 6 April 1968, before its release. The album was also the first of several to feature cover artwork by Hipgnosis. The following year, the band released a soundtrack album (More) and the live / studio hybrid Ummagumma. The following year's Atom Heart Mother was a collaboration with Ron Geesin featuring an orchestra and choir, with Meddle and the Obscured by Clouds soundtrack following in 1971 and 1972, respectively. The band achieved worldwide commercial success with The Dark Side of the Moon (1973), which has sold more than 30 million copies and is one of the best-selling albums in the world. It has been reissued as a Quadrophonic LP and 5.1 surround sound Super Audio CD. The Dark Side of the Moon was followed by Wish You Were Here (1975), Animals (1977), and The Wall (1979); all except Animals reached number one in the US, and The Wall is the highest-certified multiple-disc album by the Recording Industry Association of America. Pink Floyd released few singles after Barrett's departure, though "Money" was a US top 20 hit, and "Another Brick in the Wall, Part 2" was a number one hit in the UK and US. Bassist and singer Roger Waters gradually became the dominant and driving force in the band from the mid-1970s until his departure from the group in 1985, declaring Pink Floyd "a spent