It was also lead writer Roger Waters' idea to split "Shine On You Crazy Diamond" into two parts and use it to bookend the album around three new compositions, introducing a new concept as the group had done with their previous album, The Dark Side of the Moon. As with The Dark Side of the Moon, the band used studio effects and synthesizers, and brought in guest singers to supply vocals on some tracks off the album. These singers were Roy Harper, who provided the lead vocals on "Have a Cigar", and the Blackberries, who added backing vocals to "Shine On You Crazy Diamond". Wish You Were Here was an instant commercial success (despite the fact that Harvest Records parent company EMI was unable to print enough copies of the album to satisfy commercial demand), and although it initially received mixed reviews, the album has since gone on to receive critical acclaim. It appears on Rolling Stone's lists of "The 500 Greatest Albums of All Time" and the "50 Greatest Prog Rock Albums of All Time". Band members Richard Wright and David Gilmour have cited Wish You Were Here as their favourite Pink Floyd album, and many critics and fans have considered the album to be the band's magnum opus.