On August 29, 1970

Saturday at the 1970 Isle of Wight Festival started at lunchtime with a two-hour solo set by John Sebastian during which, after delivering “Daydream”, “Nashville Cats”, “You’re a Big Boy Now” and others, he was unexpectedly joined by his former Lovin’ Spoonful colleague Zal Yanovsky, who had sent a note up to the stage asking to be invited to join in. Together they ran through some more of the Spoonful’s hits, including “Do You Believe in Magic” and the gorgeous “Darling Be Home Soon”. Sebastian finished off with “Younger Girl” and “Red-Eye Express”, leaving the crowd feeling beatific at the start of a day of unbroken sunshine.

An hour and half later came a different kind of singer-songwriter: Joni Mitchell, three albums into her career, already known for “Chelsea Morning”, “Both Sides, Now”, “Woodstock” and “Big Yellow Taxi”, wearing a long dress the colour of goldenrod, a few shades darker than her hair, and a discreet assortment of silver and turquoise jewellery. And she was about to face an ordeal that no one present would forget.

She came on with her guitar and began with “That Song About the Midway”. “Chelsea Morning” was next, but as she started the third verse she appeared to lose her way. After strumming on for a few more bars, she announced: “I don’t feel like singing that song so much.” She gave a little laugh and got a round of sympathetic applause, but already the strain of being alone on the stage in front of more than half a million people, delivering such intimate music, was beginning to tell, and her unease seemed to communicate itself to the crowd.

It’s hard to get that many people to be completely silent on a sunny afternoon. Her next little speech expressed annoyance. “When I hear someone saying, ‘Joni, smile for Amsterdam!’ it really puts me off and I get uptight and I forget the words and I get really nervous and it’s a drag. Just give me a little help, will you?” And then just as announced that she was going to play “Woodstock”, a disturbance in front of the stage led her to stand up and move away as a stoned boy was removed from the crowd.

She sat back down and started again. As she finished the song, a bearded man in a dark T-shirt who had been crouching behind the piano rose to his feet and asked if he could use her microphone. He wanted to make an announcement to the people in the encampment on the hill beyond the perimeter fence. Elliot Roberts, Mitchell’s manager, led a group of half a dozen people who quickly surrounded him and moved him away from the singer.

All the tensions of the weekend were coming to the surface. Some of the people in the crowd had chanted “Let him speak!” Was a rock festival a commercial enterprise or a free-for-all? Were the anarchists and situationists and freaks right to try and tear down the fences? Rikki Farr, the organisers’ spokesman, sensibly ordered the uniformed security guards to leave the stage. But how, in 1970, were you supposed to deal with a moment like that? For a minute, even in that brilliant Saturday sunshine, the atmosphere was closer to Altamont than Woodstock.

Shaken but determined to continue, Mitchell tried to resume her performance. Behind her back, the bearded man was finally being dragged away, and the crowd didn’t like the way it was done. So she stopped and made another speech, an angry and distressed plea for the chance to do her work: “Last Sunday I went to a Hopi ceremonial dance in the desert and there were a lot of people there and there were tourists who were getting into it like Indians and Indians who were getting into it like tourists, and I think that you’re acting like tourists, man. Give us some respect!”

It was brave, and it worked. She was able to complete her performance in relative peace, the crowd now more attentive and the atmosphere lightened appreciably by “Big Yellow Taxi”. Having been led away by Roberts at the end of the set, the sound of cheering brought her back for encores that washed away the memory of the earlier interruptions.

And that was just the start of an extraordinary sequence. Here’s what I wrote in the Melody Maker about the next performer: “Mr Herbert Khaury, alias Tiny Tim, alias Larry Love the Singing Canary, bounded on stage to sing ‘a few tunes from the early part of the century.’ Blowing kisses to the audience and strumming his ukelele, he seemed unlikely to retain the audience’s interest for long. But his rock and roll medley, with some of the most untogether playing ever heard (‘This is my wonderful English band… my wonderful English band’) was very amusing. The master stroke was his final medley of ‘There’ll Always Be an England’ and ‘Land of Hope and Glory’, which somehow got the audience on its feet to sing these ridiculously patriotic songs.”

Tiny Tim’s bizarre bonhomie had removed the last trace of bad vibes. While the road crew rearranged the stage, Jeff Dexter, the festival’s DJ, made two crowd-pleasing choices: Otis Redding’s “Respect” and Free’s “All Right Now”, during which a multicoloured hot-air balloon floated above the crowd, its two occupants exchanging peace signs with the mass of humanity below.

Now it was late afternoon, and into the last rays of the sun slid Miles Davis, a 44-year-old jazz trumpeter who had served his apprenticeship almost a quarter of a century earlier with Charlie Parker and now faced the challenge of captivating 600,000 hippies. He took the stage in a thin red leather jacket over an orange knitted top, with studded blue jeans and silver boots. His sidemen — the saxophonist Gary Bartz, Chick Corea and Keith Jarrett on electric keyboards, Dave Holland on bass guitar, Jack DeJohnette on drums and Airto Moreira on percussion — had come as they were.

In August 1970 Miles was moving from a freer version of the complex music his quintet played in the second half of the ’60s to a direct engagement with funk. He’d already played to young audiences at the Fillmores in San Francisco and New York, on bills with the Grateful Dead and the Steve Miller Band. But the ties to the earlier music were not yet cut. The rhythm section he brought to the Isle of Wight ensured that however groove-centred the music became, it retained its freedom and complexity.

An unbroken set alluded to five compositions from the previous couple of years — “Directions”, “Bitches Brew”, “It’s About that Time”, “Sanctuary” and “Spanish Key” — before finishing with a fragment of his usual fanfare. Shrewdly, he played for barely 35 minutes: enough to intrigue and even beguile the hippies who didn’t know his music, not enough to try their patience.

The opening salvo took no prisoners. Miles wanted the music to burn, and he was concentrating hard as he led the way with fierce stabs and insolent runs on his lacquered instrument. The stage was bracketed by Jarrett, on an RMI keyboard that gave him the sounds of an electric piano and an organ, and Corea, who had what looks like a ring modulator on the top of his Hohner instrument and used it to make bleeps and squiggles of sound. Holland brought a jazz musician’s inventiveness to the funk bass lines, which was not what Miles would ultimately want, but there was a passage when he and DeJohnette meshed into a kind of broken second-line rhythm that lifted the music right up. Bartz flighted his brief soprano and alto solos with a keening sound and a striking trajectory, while Airto added the exotic noises of the shaker, the pandeira, the agôgo, and the cuica, a Brazilian friction drum with a distinctive whooping sound.

Miles prowled the stage, never far from the action. A quarter of an hour in, midway through “It’s About that Time”, virtually unrecognisable from its treatment on In a Silent Way a year earlier, the music took off. As it seethed and roiled, Miles returned to centre-stage and played two short, quiet phrases that redirected everything. Then he sketched the exposed theme of “Sanctuary” before cueing up the riff of “Spanish Key”.

He let the band get on with it for five minutes before raising his horn and lowering it back to the microphone, the signal for the funk to back off and textures to be laid over the simmering pulse behind his exquisite open-horn phrases, some of the them hinting at old Moorish influence. As he returned to the staccato jabs, the rhythm section, which had been simmering quietly, rose up again in response, coming back to the boil.

And suddenly the time was up. The music shuddered towards a halt. While the rhythm section wound down, Miles bent down to pick up his silver mute, waved his trumpet once to the crowd, grabbed his shoulder bag and his jacket, and was gone, into the dusk, leaving us to talk about the extraordinary nature of what we’d heard, and what it meant to hear it in the context of a giant rock festival. When they asked him the names of the pieces he’d played, he said, “Call it anything.”

* The full sets by Joni Mitchell and Miles Davis are on YouTube, filmed by Murray Lerner for his documentary on the festival. Miles’s set can also be found on the album Bitches Brew Live, released in 2011 by Columbia Legacy, and on Electric Miles: A Different Kind of Blue, an Eagle Rock DVD from 2004.