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,
Concept album Moore says that "Even though previous albums had set a unified mood, it was on the basis of the influence of "Sgt. Pepper" that the penchant for the concept album was born." Adding to "Sgt. Pepper"s claim, the artwork reinforced its central theme by depicting the four Beatles in uniform as members of the Sgt. Pepper band, while the record omitted the gaps that usually separated album tracks. Author Bill Martin relates the assumed concept albums of the 1960s to progressive rock: "Popmatters" Sarah Zupko notes that while the Who's "Tommy" is "popularly thought of as the first rock opera,