The Wall is the 11th studio album by Pink Floyd, originally released in November 1979. It is the last studio album released with the line-up of guitarist David Gilmour, bass guitarist/lyricist Roger Waters, keyboardist Richard Wright, and drummer Nick Mason before Wright left the band. As with Pink Floyd's prior three albums, The Wall is a concept album, exploring themes of abandonment and personal isolation. It is a rock opera that follows Pink, a character whom Waters modelled after himself and the band's original leader, Syd Barrett. Waters conceived the album during Pink Floyd's 1977 In the Flesh Tour, when his frustration with the audience became so acute that he imagined a wall between the audience and the stage. The album was one of the best-selling of 1980, and by 1999 it had sold over 23 million RIAA-certified units, making it the third highest certified album in the United States.