Despite its legendary status, not everyone champions Woodstock as Jimi Hendrix’s greatest performing hour. His recreation of ‘The Star Spangled Banner’ may be his most inspirationally symbolic moment, the three minutes when Sixties pop truly became transfiguring art but his most recent biographer, John McDermott isn’t the first to question the merit of the music that preceded it. At last, the official release of these tapes supplies the evidence for judgement.

It’s true that circumstances weren’t ideal. In the hours before, Hendrix had been unwell while he brought to Woodstock an untested band with drummer Mitch Mitchell flanked by two fledgling percussionists and old friends, bassist, Billy Cox and secondary guitarist, Larry Lee who were still feeling their way into his new musical presence.

Certainly Woodstock has its disposable moments, notably ‘Jam Back At The House’, a repetitious musicians’ equivalent of a meditational exercise. It may have been therapeutic for those within the ritual but now can sound useless to those without.

Mostly Hendrix plays his own version of the blues and at times - especially ‘Hear My Train A’ Coming’ – it’s as if he’s digging his pick into hard, unyielding and compacted ground. The chiselling is furious but the sculpture doesn’t always form. The intensity of the quest not the discovery of a destination impresses.

‘Fire’ scalds as an opening salvo; ‘Voodoo Child (Slight Return)’ doesn’t disappoint in its ferocity, but the wonder of Hendrix’s performance in these pre-packaged days is the way Hendrix takes improvisation for granted. He’s almost chastising and punishing the blues as a warm-up for his eventual attack on the peak, his own exercises before scaling Everest.

But then the alternative anthem. Jazzmen used to practice their most sublime gymnastics round Tin Pan Alley and Broadway standards but Hendrix isn’t out to prove he could pirouette. His reworking of the American anthem endures because it’s more than just rock’s most spectacular example of instrumental agitprop since he also uses all the resources of his own tradition to wrestle bourgeois classicism into total and abject submission. This, Hendrix is saying is what American music really is if only the elite in the opera-seats would listen.

But it isn’t an isolated peak. ‘Woodstock’ also rescues the music that followed, an awesome solo improvisation that’s one part flamenco and the other part Arabic; that’s another sad hint of the unfinished artistic business left after his death. The with ‘Villanova Junction’, he resolves all the previous savagery into sweetness. The mountaineer is replaced by the sky-diver drifting down from heaven.

Woodstock would, of course, inaugurate the outdoor concert as a predictable and manageable spectacle, but in the late Sixties not even the artist really knew what might happen next and creativity still bonded with hazard. Get it for ‘The Star Spangled Banner’ but also for the preceding moment when you hear the true blood, sweat and tears of a story struggling to be told.