"A decade ago prog was the preserve of the diehard. Now  is set to be a glorious summer of prog."
Nick Shilton, Classic Rock Presents: Prog!
Between June and September 2011, bands such as Caravan, Arena, Focus, Wishbone Ash, Magma, Jethro Tull, Dream Theater, Spock's Beard, Hawkwind, Supertramp, and Van der Graaf Generator (to name a few) descended upon England either as part of multi-legged tours, or during extravagant Progressive Rock festivals (oftentimes, both). Progressive Rock is again quasi-popular, prompting further analysis of its original popularity, the reasons for its decline and its resurgence(s). Progressive Rock, while not a widespread culturally enduring genre of music, is one of the most technical and genuinely artistic forms of rock music. Progressive Rock came about by a greater desire for intellectualism in popular music, primarily through technical ability and artistry inherent of the genre; similar reasons for its decline are the associated elitism, and the intrinsic nature of popular entertainment. Fundamentally, progressive rock transcends genre and style, reaching across virtually every musical discipline.
Britannica defines 'progressive rock' as "'intellectual' album-oriented rock [...] either classically influenced [...] employ[ing] complicated and conceptual approaches to music." Progressive rock (casually abbreviated to 'prog', which includes all progressive sub-genres including but not limited to progressive metal, progressive folk, zeuhl, as well as certain space rock, fusion and psychedelic albums). As shown by Britannica's definition, it is far easier to define the genre qualitatively (through tendencies) than through labels.
Throughout the 1960s, psychedelic music was emerging from conventional rock 'n' roll combined elements of jazz, blues and local folk, yet suffered from a distinct lack of vision. An early Pink Floyd track, Interstellar Overdrive, suffered from this same flaw. The track starts with its main theme, which builds for the first few minutes. As the track progressives, the track flows away from the theme, featuring intermittent jerks and noises for several minutes (the bulk of the song), before petering out. A critical part of psychedelia was this `jam`, where the musicians would tie together various improvisations to arrive at an extended piece of music.
This sporadic juxtaposition of musical sentiment posed a challenge to mainstream audiences. The 1968 song of the year was "Little Green Apples" by O.C. Smith, a country song that followed a 4/4 verse-chorus structure (as was dominant in popular music). Edward Macan identifies that progressive music, despite having its roots in psychedelia "solve[s] yet another challenge posed by the psychedelic jam - how to create a sense of direction - by drawing on nineteenth-century symphonic music's fondness for building up tension until a shattering climax is reached, abruptly tailing off, and then starting the process anew."