George Roger Waters (born 6 September 1943) is an English musician, singer-songwriter and composer. He was a founder member of the progressive rock band Pink Floyd, serving as bassist and co-lead vocalist. Following the departure of bandmate Syd Barrett in 1968, Waters became the band's lyricist, principal songwriter and conceptual leader. The band subsequently achieved international success in the 1970s with the concept albums The Dark Side of the Moon, Wish You Were Here, Animals and The Wall. Although Waters' primary instrument in Pink Floyd was the bass guitar, he also experimented with synthesisers and tape loops and played rhythm guitar on recordings and in concerts. Amid creative differences within the group, Waters left Pink Floyd in 1985 and began a legal battle with the remaining members over their intended use of the group's name and material. They settled the dispute out of court in 1987, and nearly eighteen years had passed before he performed with Pink Floyd again. The group have sold more than 250 million albums worldwide, including 74.5 million units sold in the United States as of 2012[update].