KEY POINTS:
Here is a great lost moment from pop cultural history: a pop group called Them perform for an audience of screaming teenagers at the NME Poll Winners' Concert of 1965.
The venue is Alexandra Palace in London, the compere is disc jockey Jimmy Savile, wearing what looks like a mod smock.
His introduction begins like this: "Hi di hi, he hi he hi, hi hoi! Ladies and gentlemen, the next group has just finished doing a tour of one-night stands with the Luton girls' choir, and they're going to have to leave the country very shortly."
The group stroll on stage. They perform their latest chart hit, Here Comes the Night, to a chorus of screams. The singer is the teenage Van Morrison, tight-jeaned, his long, wavy hair styled in a side parting. He could not look more uninterested.
Then they do a cover of Bobby Bland's Turn On Your Love Light, which lasts an incredibly long time.
The screams fade to a bemused silence as Morrison howls the blues in a way that makes you realise why the late John Peel once described him as the only white singer allowed to shout "Lord, have mercy!" on his show.
Apart from a few clips from the Sixties pop programme Ready, Steady, Go, it is perhaps the only surviving fragment of Them at their primal best.
Here is another even more surreal lost moment from pop cultural history: the soul singer and soon-to-be recluse Sly Stone being interviewed by Dick Cavett on the latter's prime-time American chat show in July 1970.
Dick wears a grey suit and matching tie: Sly also wears a suit, but it is a bright red sequined creation, topped and tailed by knee-high, diamond-studded boots and a big, woolly, floppy hat that sits unsteadily atop his afro.
Dick is every inch the straight guy, Sly is loaded.
Dick: I heard you had some trouble getting here.
Sly, staring intently at his index finger: Yeah, I had my house broken into.
Dick: You've cut yourself there. How did it happen?
Sly: I broke into my house.
The interview never really recovers. On the same show, Sly and the Family Stone overcome a staid studio setting with a propulsive performance of Thank You (Falettinme Be Mice Elf Agin) and you cannot help but think that they were the greatest live act ever.
Both of these performances have appeared out of the mists of time and, as if by magic, on YouTube in the past year. Though its younger users tend to spend their time viewing and rating the endless hours of amateur footage posted on YouTube, for viewers of a certain age, the video-sharing website is fast becoming the most extensive repository of great lost moments from pop cultural history.
In the past year, I have received regular emails from friends alerting me to the presence of yet another extraordinary Neil Young live clip, or some rare footage of Joy Division in a pub near Manchester, England.
Where does this stuff come from? Who posts it on YouTube? Why have we not seen it before now? Mostly, it comes from the vaults of long-lost TV shows, the archives of record labels.
Some is posted by fans who secretly filmed gigs, or by insiders who filmed bands in rehearsals and during live shows and, sometimes, by ordinary people who filmed their favourite pop group by pointing a camera at the TV.
It is appearing now because the internet, and YouTube in particular, is the perfect medium not just for inspired amateurs who want to parade their otherness, but for the kind of pop cultural excavation that would have been prohibited - or punished - by the major record labels in the days before the world wide web.
Since YouTube's inception in February 2005 it has changed the way we look at pop history.
Last year, the big four record companies, Warners, EMI, Universal and Sony BMG, suddenly aware that history was about to leave them behind, all agreed to allow YouTube, which is now owned by Google, to have access to all of their music videos free of charge in exchange for a share of the advertising revenue generated.
Much of the stuff I have been enthralled by, though, belongs to a time before the advent of the big-budget pop promo video, before MTV colonised, and dulled, our imaginations in the Eighties.
Taken together, many of these often grainy performances, films, short clips and interviews form a kind of secret archive of pop, a fragmented history of a culture in its ascendancy.
On YouTube pop is a gloriously random, fragmented, elusive entity.
- Observer
Top 10 YouTube pop classics
1. Chuck Berry introduces the Ronettes on his 60s TV show. The godfather of rock'n'roll, three foxy chicks, one epic song (Be My Baby). And some of the best frugging you'll ever see.
2. Iggy and The Stooges: Live in Cincinnati, 1970. The Stooges grind out TV Eye, while Iggy disappears into a sea of bodies for ages, then reappears holding a large jar of peanut butter, which he proceeds to smear on his torso.
3. The Cake: You Can Have Him, performance from 1967. The grooviest chicks on YouTube. The Cake were a truly fab 60s three-piece girl group, comprising Chelsea, Barbara and Jeanette. They looked like they had an expense account at Biba, and sang like angels.
4. Neil Young busking outside Glasgow Central Station, Scotland 1976. Neil takes time off from his touring schedule to go walkabout in Glasgow. He asks a businessman for directions to the Bank of Scotland, then entertains bemused passers-by with his trusty banjo and a stark version of The Old Laughing Lady. Grainy but engrossing.
5. Bob Dylan shares a taxi with John Lennon 1966. An out-take from D.A. Pennebaker's little-seen documentary, Eat the Document. A strung-out Bob barely holds it together: "I wish I could speak English, man." Lennon: "Me too, Bob."
6. Joy Division play a gig at a pub in Altrincham, 1979. Malcolm Whitehead's dark and evocative Super 8 film of an early Joy Division gig captures Ian Curtis at his most mesmerising.
7. The Grateful Dead play the Playboy Mansion, 1969. Surreal moment when the Dead and their entourage pitch up at Hugh Hefner's house and regale the bow-tied guests and Bunny Girls with a rousing St Stephen.
8. Nirvana rehearse in a garage in Aberdeen, Washington, 1988. A Dave Grohl-less Nirvana let rip in the garage of Krist Novoselic's mum's house. Love Buzz, Scoff and About A Girl all get a good kicking. Kurt sings into the wall. The grassroots of grunge.
9. The Flying Burrito Brothers, 1969. Ultra-rare footage of the late Gram Parsons, country-rock pioneer. A live version of Christine's Tune with footage of the group hanging out in the desert with the girls from the cover of The Gilded Palace of Sin album.
10. David Bowie is given a karate lesson on the Dinah Shore show, 1975. Bowie in his Thin White Duke phase somehow ends up having a karate lesson on American TV. A black dude throws shapes and asks Bowie what he'd do if "I was coming at you to choke you". Bowie says: "I'd scream very loudly." Priceless.
