pop, a separation which was "also, broadly, one between boys and girls, middle-class and working-class." Before progressive/art rock became the most commercially successful British sound of the early 1970s, the 1960s psychedelic movement brought together art and commercialism, broaching the question of what it meant to be an artist in a mass medium. Progressive musicians thought that artistic status depended on personal autonomy, and so the strategy of "progressive" rock groups was to present themselves as performers and composers "above" normal pop practice. "Proto-prog" is a retrospective label for the first wave of progressive rock musicians. The musicians that approached this genre harnessed modern classical and other genres usually outside of traditional rock influences, longer and more complicated compositions, interconnected songs as medley, and studio composition. Progressive rock itself evolved from psychedelic/acid rock music, specifically a strain of classical/symphonic rock led by the Nice, Procol Harum, and the Moody Blues. Critics assumed King Crimson's debut album In the Court of the Crimson King (1969) to be the logical extension and development of late 1960s proto-progressive rock exemplified by the Moody Blues, Procol Harum, Pink Floyd, and the Beatles. According to Macan, the album may be the most influential to progressive rock for crystallizing the music of earlier "proto-progressive bands [...] into a distinctive, immediately recognizable style". He distinguishes 1970s "classic" prog from late 1960s proto-prog by the conscious rejection of psychedelic rock elements, which proto-progressive bands continued to incorporate. Post-progressive "Post-progressive" is a term invented to distinguish a type of rock music from the persistent "progressive rock" style associated with the 1970s. In the mid to late 1970s, progressive music was denigrated for its assumed pretentiousness, specifically the likes of Yes, Genesis, and Emerson, Lake & Palmer. According to musicologist John Covach, "by the early 1980s, progressive rock was thought to be all but dead as a style, an idea reinforced by the fact that some of the principal progressive groups has developed a more commercial sound. [...] What went out of the music of these now ex-progressive groups [...] was any significant evocation of art music." In the opinion of King Crimson's Robert Fripp, "progressive" music was an attitude, not a style. He believed that genuinely "progressive" music pushes stylistic and conceptual boundaries outwards through the appropriation of procedures from classical music or jazz, and that once "progressive rock" ceased to cover new ground – becoming a set of