Revolver (Beatles album) as the Beatles'. While also highlighting the importance of the production, David Howard writes that "Revolver" was a "genre-transforming album", on which Martin and the Beatles had "obliterated recording studio conventions". Combined with the similarly "visionary" work of American producer Phil Spector, Howard continues, through "Revolver", the recording studio had become "its own instrument; record production had been elevated into art." Whereas "Sgt. Pepper" had long been identified as the Beatles' greatest album, since the 2000s "Revolver" has often surpassed it in lists of the group's best work. Sheffield cites the album's 1987 CD release, with the full complement of
Rarities (Beatles compilations) as part of "The Beatles Collection" box set. Most of the tracks on the "Beatles Collection" disc titled "Rarities" were already available on American Beatles LPs. As a result, Capitol assembled an album of Beatles tracks that were considered rare in America. They include tracks not previously issued on a Capitol or Apple LP and alternative versions of several well-known songs which were also not readily available in America. A highlight of the album was the gatefold sleeve featuring a reproduction of the original controversial "butcher" cover photo of the 1966 "Yesterday and Today" album. Although the Capitol "Rarities" album