The album was loosely conceptualised as a performance by the fictional Sgt. Pepper band, an idea that was conceived after recording the title track. A key work of British psychedelia, it incorporates a range of stylistic influences, including vaudeville, circus, music hall, avant-garde, and Western and Indian classical music. The band continued the technological experimentation marked by their previous album, "Revolver", this time without an absolute deadline for completion. With producer George Martin and engineer Geoff Emerick, the group coloured much of the recordings with sound effects and tape manipulation, as exemplified on "Lucy in the Sky with Diamonds", "Being for the Benefit of Mr. Kite!" and "A Day in the Life". Recording was completed on 21 April. The cover, which depicts the Beatles posing in front of a tableau of celebrities and historical figures, was designed by the pop artists Peter Blake and Jann Haworth.