Chapter
The seventies split into parallel markets. Prog uses odd meters, Mellotron, and multi-part suites. Hard rock bets on riff, volume, and chorus hooks. Led Zeppelin mixes acoustic/electric dynamics and long improvisation. Black Sabbath detunes and writes tritone-heavy songs that seed metal. Pink Floyd builds album-length studio concepts. King Crimson keeps dissonant structure tight. Arena touring scales with PA systems and lighting rigs. Bigger songs need bigger rooms; the economics follow.
Sound: Concept side-longs, downtuned power chords, double-kick and tom fills