Progressive Rock

Prog rock takes rock instrumentation and grafts on classical, jazz, and contemporary-music devices. Time signatures change mid-song (5/4, 7/8, 11/8, 15/16 all show up), tempos shift, and individual tracks run 10-30 minutes in suite forms. The defining keyboards are the Mellotron (a tape-replay strings/choir machine), the Hammond organ, and the Moog synthesizer. Lyrics work in mythology, science fiction, literature, and philosophy. Vocals range from spoken-baritone narrator to operatic soprano. Production aimed for studio-art status — every channel is precisely placed in the stereo field.

The form coalesced in Britain in 1968-70: The Moody Blues' 'Days of Future Passed' (1967), King Crimson's 'In the Court of the Crimson King' (1969), early Pink Floyd, Yes, Genesis, Emerson Lake & Palmer (1970), and Jethro Tull all appeared within a few years. The golden run was 1971-77, with Yes's 'Close to the Edge' (1972), Pink Floyd's 'The Dark Side of the Moon' (1973), Genesis's 'The Lamb Lies Down on Broadway' (1974), and King Crimson's 'Red' (1974) as touchstones. Punk's 1977 backlash framed prog as bloated and bourgeois, and the genre collapsed commercially within two years. A later generation — Marillion, Dream Theater, Tool — has carried the form forward.

Time-signature changes are the genre's central pleasure: Yes's 'Heart of the Sunrise' moves between 11/8 and 4/4, King Crimson's 'Discipline' layers 17/16 against 15/16. Listen for how the keyboards layer (Mellotron strings under Hammond organ under Moog lead). Concept-album structure — recurring motifs across an LP-length sequence — pays off only if you listen front to back. Keyboard players (Rick Wakeman, Keith Emerson, Tony Banks) are often the most-watched member of the band.

Pink Floyd's 'The Dark Side of the Moon' (1973) is the most-accessible entry — 43 minutes, gapless transitions, 50+ million copies sold. For the harder edge, King Crimson's 'In the Court of the Crimson King' (1969); for the suite-form approach, Yes's 'Close to the Edge' (1972).

'The Dark Side of the Moon' has charted on the US Billboard 200 for a cumulative 950+ weeks — by far the longest of any album in history (the count is non-consecutive but covers fifty years). Rick Wakeman performed Yes's 1974 'Tales from Topographic Oceans' tour surrounded by a semicircle of Mellotrons, Minimoogs, and Hammond organs in numbers that became part of prog folklore.