Matthew Bannister traces "the more self-conscious, camp aesthetic of art rock" to pop artist Andy Warhol and the Velvet Underground, who emulated Warhol's art/pop synthesis. Accordingly: "Warhol took Spector's combination of the disembodiment, 'distance' and refinement of high culture with the 'immediacy' of mass cultural forms like rock and roll several stages further ... But Warhol’s aesthetic was more thoroughly worked out than Spector's, which represented a transitional phase between old-fashioned auteurism and the thoroughly postmodern, detached tenets of pop art. ... Warhol's approach reverberates throughout art rock, most obviously in his stance of distance and disengagement." In 1969, the Doors also explored art rock genre on their fourth album, The Soft Parade. Influential albums 1965–66 The December 1965 release of the Beatles' Rubber Soul signified a watershed for the pop album, transforming it in scope from a collection of singles with lesser-quality tracks to a distinct art form, filled with high-quality original compositions. The album garnered recognition for the Beatles as artists from the American mainstream press, anticipating rock music's cultural legitimization as an art form. Writing in 1968, Gene Sculatti of Jazz & Pop recognized Rubber Soul as "the definitive 'rock as art' album" and "the necessary prototype" that major artists such as the Rolling Stones (with Aftermath) and the Beach Boys had felt compelled to follow. The period when rock music became most closely aligned with art began in 1966 and continued until the mid 1970s. Academic Michael Johnson associates "the first documented moments of ascension in rock music" to the Beach Boys' Pet Sounds and the Beatles' Sgt. Pepper's Lonely Hearts Club Band (1967). Released in May 1966, Pet Sounds came from Wilson's desire to make a "complete statement", as he believed the Beatles had previously done with Rubber Soul. In 1978, biographer David Leaf wrote that the album heralded art rock, while according to The New York Observer, "Pet Sounds proved that a pop group could make an album-length piece comparable with the greatest long-form works of Bernstein, Copland, Ives, and Rodgers and Hammerstein." Pet Sounds is also noted as the first rock concept album. In 1971, Cue magazine described the Beach Boys as having been "among the vanguard" with regard to art rock, among many other aspects relating to the counterculture, over the period up to late 1967. Jacqueline Edmondson's 2013 encyclopedia Music in American Life states that, although it was preceded by earlier