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>
Greatest Hits Volume 1 (Beatles album) original 1965 stereo mixes of "I Want To Hold Your Hand" rather than the new stereo mixes created for the late-1966 compilation album "A Collection of Beatles Oldies". The mono editions of the album feature fold-down mono mixes, with only "She Loves You" and "I'll Get You" appearing in true mono, due to the unavailability of stereo mixes at the time of the compilation. The cover art was borrowed from the U.S. Beatles album, "Beatles IV" with the back cover using elements from the German album "The Beatles Beat". The mono version of Greatest Hits Volume 1 was released in