Caravan's fourth album was a bit of a departure: Richard Sinclair brought in new keyboard player Steve Miller, previously in Delivery, to "jazz" up the Caravan sound. "Waterloo Lily," a song about a heavy-set hooker, would be one of the last songs Sinclair would sing with the band. It's a simple number, but Miller's extended electric piano solo signals the change.

In protest over the misconception of Aqualung (he claimed it wasn't a concept album), Ian Anderson delivered what might be the mother of all concept albums: the wryly-titled Thick As A Brick. Based on a "poem written by eight-year-old Gerald Bostock and set to musical accompaniment by rock group Jethro Tull," the album contains a single "song" spanning both sides of the vinyl. So much for the approach pioneered on Aqualung!

The Strawberry Hill Boys were a bluegrass trio founded by Dave Cousins, Tony Hooper and Ron Chesterman in 1967. Sandy Denny briefly passed through the band, recording an unreleased album (1973’s All Our Own Work) before joining Fairport Convention. In 1969 the band shortened their name and landed a recording contract with A&M. The Strawbs recorded two early albums with production heavyweights Gus Dudgeon and Tony Visconti, respectively. In 1970, Chesterman left, and Cousins and Hooper added the rhythm section of John Ford and Richard Hudson.

English progressive rock was hugely popular in Italy during the early 70s, so it was only a matter of time before the Italians themselves decided to create progressive music as well. Premiata Forneria Marconi ("Award Winning Marconi Bakery") were at the forefront of this movement. Originally the beat group I Quelli, the members had enjoyed relative success in Italy as both a support band for others and as session musicians.

Ex-Yes guitarist Peter Banks was enlisted for a (very) short stint in Blodwyn Pig before forming Flash. True to their name, Flash appeared quickly, released three albums for Capitol Records and vanished. Banks recruited vocalist Colin Carter, bassist Ray Bennett and drummer Mike Hough, with ex-Yes keyboardist Tony Kaye filling in on their debut.

Though fusion could be described as the combination of jazz and rock, it may be more accurate to acknowledge its rise as “when jazz got electric.” Mahavishnu Orchestra was definitely electric, perhaps even manic at times.

Gong had now solidified from a loose amalgamation of Paris fringe musicians to a relatively stable touring unit. Daevid Allen, accompanied by partner Gilli Smyth and saxophonist Didier Malherbe, added Pip Pyle on drums and Christian Tritsch on bass; and the band completed their first return to England with a performance at the Glastonbury Festival in June 1971. Kevin Ayers also served a six-month tour duty around this time, leaving a John Peel Session as his recorded legacy with the band. Gong recorded three albums in 1971.

Beginning on April 12th, 1971, at the Zoom Club in Frankfurt, Germany, King Crimson returned to live performance with a lineup comprised of Robert Fripp, Mel Collins and newcomers Ian Wallace (ex-The Warriors) on drums and Boz Burrell on vocals, with Pete Sinfield back-of-the-house on VCS3 synthesizer and lights. Per legend, auditions for bassists proved so unsuccessful that Fripp eventually taught Burrell how to play the instrument. The band toured extensively, breaking only to record their fourth album, Islands.

After their triumphant return, Traffic assembled a live unit with two members from Ginger Baker’s Airforce, bassist Ric Grech and percussionist Reebop Kwaku Baah. Drummer Jim Gordon came in to allow Jim Capaldi to concentrate on vocals. Even Dave Mason returned for a few gigs in mid-1971, as documented on the interim live album, Welcome To The Canteen. However, the oddly titled The Low Spark Of High Heeled Boys was another masterpiece for the band.

Led Zeppelin was already a household name by 1971, due in part to Jimmy Page’s huge guitar riffs and singer Robert Plant’s voice and good looks. Their first two albums were mostly hard rock rip-offs of blues standards-albeit excellent hard rock rip-offs of blues standards. Their third album, however, stretched out musically, particularly with British folk influences; that’s further exploited here on “The Battle of Evermore,” a vocal duet with Fairport Convention’s Sandy Denny.