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 of 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". The album became an instant commercial success and record company EMI was unable to print enough copies to satisfy demand. Although it initially received mixed reviews, the album has since been acclaimed by critics and appears on Rolling Stone's list of "The 500 Greatest Albums of All Time". Band members Richard Wright and David Gilmour have each cited Wish You Were Here as their favourite Pink Floyd album, and the album is widely regarded as the group's magnum opus