Revolver (Beatles album) group collective since 1962, and gave them an unprecedented amount of time to prepare for a new album. Writing in "The Beatles Forever", Nicholas Schaffner cites 1966 as the start of the band's "'psychedelic' period" and adds: "That adjective implies not only the influence of certain mind-altering chemicals, but also the freewheeling spectrum of wide-ranging colors that their new music seemed to evoke." Music journalist Carol Clerk describes "Revolver" as having been "decisively informed by acid", following John Lennon and George Harrison's continued experimentation with the drug LSD since the spring of 1965.<ref name="Clerk/Uncut"> Available at Rock's Backpages (subscription required).</ref>
The Beatles (album) stereo only. In the UK, the following album, "Yellow Submarine", was the last to be shipped in mono. The mono version of "The Beatles" was made available worldwide on 9 September 2009, as part of "The Beatles in Mono" CD boxed set. A reissue of the original mono LP was released worldwide in September 2014. The album's sleeve was designed by pop artist Richard Hamilton, in collaboration with McCartney. Hamilton's design was in stark contrast to Peter Blake's vivid cover art for "Sgt. Pepper's Lonely Hearts Club Band", and consisted of a plain white sleeve. The band's name, in Helvetica,