The ’70s was the high-water mark of rock’n’roll excess, the decade in which pop musicians, swollen with wealth and steeled by ruthless managers, realised the power they wielded, and flaunted it shamelessly. As cocaine inflated the self-esteem of semi-literate stars, the most ridiculous and half-baked of notions were indulged in sprawling, quasi-philosophical concept albums clad in ghastly gatefold sleeves, and the ham-fisted, overblown caterwaulings of redneck boogie-bands lovingly documented in live double albums of mind-numbing banality.

Backstage, the morality envelope was stretched to breaking point by the hedonistic exploits of touring musicians while, out stagefront, increasingly extravagant and costly spectacles separated these self-proclaimed rock gods ever further from the fans with whom they had once shared some tenuous fellowship. A few years before, you could have watched Eric or Elton or Duane or Jimmy from a few yards away in the fevered atmosphere of a small club; by 1975, you were lucky if you could see them at all from Row ZZ, Block 126, let alone admire their dazzling fretwork. This was the dark period between the advent of stadium rock and the development of adequate big-screen technology, so if you weren’t sufficiently distracted by the giant flying pig or the hovering UFO or the scale model of Stonehenge, you were doomed to suffer, if not in silence, then at least in something approaching blindness. Bob Dylan was no less immodestly ambitious than other rock stars?indeed, his 1974 American tour with The Band had done much to establish the legitimacy of stadium rock?but his ambitions ran in different directions to most musicians.

By 1975, his re-immersion in the bohemian Greenwhich Village folkie milieu (from which he had exiled himself during the late ’60s) inspired him to embark upon the Rolling Thunder Revue, a low-key, high-concept tour, part hootenanny, part travelling minstrel show, with a posse of his old chums, including Joan Baez, Bobby Neuwirth, Roger McGuinn and Ramblin’ Jack Elliott, and a backing band combining youthful verve (notably teenage multi-instrumental virtuoso David Mansfield) with seasoned experience (former Bowie sidekick Mick Ronson).

The vibe would be spontaneous, collaborative and poetic?Ginsberg was along for the ride, too?and the whole thing would be filmed. To make the film more than just another tour documentary, though, dramatic tableaux would be improvised from town to town, with playwright Sam Shepard on hand to try and shoehorn the resulting scenes into some semblance of coherence.

The Rolling Thunder Revue itself may have been a deliberately low-level, freewheelin’ undertaking, but at nearly four hours long, the resulting movie, Renaldo & Clara, would ultimately rank as one of the decade’s greatest rock-star indulgences, Dylan’s own giant flying pig. “It’s about the essence of man being alienated from himself and how, in order to free himself, to be reborn, he has to go outside himself,” he tried to explain, but few were persuaded: mauled by critics for its am-dram theatrics and self-regarding inscrutability, the film was soon pulled from cinemas, and rarely screened again after its initial run. The music has likewise languished in bootleg limbo for the best part of three decades before finally appearing overground. For all its legendary status, it’s a bit of a curate’s egg, with a few transcendent moments?mostly Bob’s solo versions of “Mr Tambourine Man”, “It’s All Over Now, Baby Blue”, “Tangled Up In Blue” and particularly “Simple Twist Of Fate”, all of which profit from the air of impassioned intimacy which infuses his delivery?and rather too many tracks spoilt either by oddly graceless and brusque vocal harmonies from Joan Baez, or by Scarlet Rivera’s incessant gypsy fiddling, of which a little goes a long way, and a lot goes way too far.

Sequenced to approximate the set?or at least, Dylan’s parts thereof?the album opens with a “Tonight I’ll Be Staying Here With You” which has undergone extensive but immaterial lyric changes (“throw my ticket in the well, throw my mattress out there too”, etc), and which he sings in a hoarse, almost angry voice somewhat at odds with the song’s compliant mood.

“It Ain’t Me Babe” and “The Lonesome Death Of Hattie Carroll” are among several numbers done in a twitchy, flamenco/country crossover style, which suits the latter song’s declamatory tone up to a point, but ultimately sabotages its impact by denying the dramatic shift required at its d