Original: As a psychedelic band led by Syd Barrett in the late 1960s , Pink Floyd had moderate mainstream success and were one of the most popular bands in the London underground music scene ; The UFO club , Pink Floyd however , Barrett 's erratic behavior eventually forced his colleagues to replace him with guitarist and singer David Gilmour .
Simplified: Singer and bass player Roger Waters gradually became the leader of the band in the mid-1970s , until 1985 when he left the group .