Earlier this week you could have caught Paul McCartney living it up at the Cavern Club. A television and Internet audience in their hundreds of millions did just that. Next week you can catch The Who once more simulating guitar destruction at Shepherds Bush. David Bowie played some drum 'n' bass at a small London venue the week before. The Rolling Stones and Blondie have finished their 1999 concerts. But never fear, Tina Turner and Tom Jones are just around the corner. The sudden, shared, impulse by celebrated post-menopausal fifty-somethings to go back to basics begs the question that rock music has diplomatically put off asking for a few decades now: is it an art form that can really be performed by middle-aged people?
McCartney, Jagger & Co aren't actually the first wave of rock'n'roll stars to return to the stage. I saw two roadies struggle on to the Wembley Arena stage with a sackful of candles when Little Richard celebrated his 60th birthday mid-concert a few years ago. But then it's easier for the creator of "Long Tall Sally" and "Tutti Frutti". Little Richard plays piano, so he can sit through the show.
Most of the post-menopausal rockers do have to keep in shape. Jagger, who remains astonishingly athletic in performance and is determined to keep his 28-inch waistline, takes a personal trainer on tour. At the Cavern, McCartney may have looked trim; but his backing band had fellow Sixties veterans, Dave Gilmour of Pink Floyd and Mick Green of The Pirates - two of the largest girths on the circuit. Without hair dye or a fitness regime, they looked less convincing singing "All Shook Up". All full up, perhaps. They looked like two mildly embarrassing grandads disgracing themselves to Top of The Pops after too much Christmas turkey.
Cliff Richard, who starts his Christmas concerts in Birmingham tonight, does not have any personal trainers, but has for years had a strict diet, eating just one meal a day and avoiding all fats. He also plays tennis every day.
Sir Cliff, clearly, carries on performing for the greater good, but others cite a variety of less-altruistic reasons for remaining on the road. One of the most unusual cases is Tina Turner. Just turned 60 with a stage act that involves enough dancing to tire out a 20-year-old, she collapses into her limousine at the end of a show.
"It's difficult for her," said an associate yesterday, "because she insists on her shows being high energy. The reason she does it, frankly, is for the money. People forget that Tina is one of the few great rock stars who doesn't get any royalties. She only ever wrote one song. And she has an expensive lifestyle with houses in Switzerland and the south of France, a penchant for fashion shops and an extended family to support."
Tina, at least, does not need a fitness regime. "She has never seen the inside of a gym," said the friend. "Her mother was half Cherokee and the Red-Indian blood seems to give her a natural energy which means she doesn't worry about dieting or exercising." And the public still wants her. Her promoters are to announce an extra date for her Wembley show next summer, shows that will guarantee her bank balance several hundreds of thousands of pounds.
McCartney thanks his vegetarianism for keeping him fit enough to rock'n'roll. That's not the only tribute to his late wife. Insiders know that last week's Cavern performance - like his latest album of rock'n'roll classics - is really just Paul singing Linda's juke-box. They were some of her favourite numbers, as well as his.
McCartney also believes that he and bands like The Stones and The Who still perform because they can. What these bands have in common is that they honed the craft of performing in clubs before they became famous, something only a tiny minority of chart bands do now. McCartney, too, is likely to be announcing a new tour in the new year.
For the Rolling Stones, pushing on is a matter of pride. "They love to put two fingers up to people who say they are past it," says an insider. "Nothing gave them greater pleasure than the recent Billboard table of the highest grossing tours of all time they are numbers one, two and three. And they do love performing. When they're up there they can feel that they're still scallywags. But they pace themselves now. Even Keith, who doesn't exactly move about too much on stage is learning to pace himself."
The return of The Who - arguably the greatest and highest-energy live band at their peak - is odder. Roger Daltrey told me a few years ago that he hated it that the band were not playing live - as without that "the music dies". When I reported this to Pete Townshend, he shouted at me: "Roger wants me to get up with him and re-live our youth. Well, I won't do it."
Evidently, Townshend has changed his mind. Next week The Who return to where they grew up, Shepherds Bush in west London, to play The Empire. Perhaps Townshend wants to keep his singer happy, though such goodwill has not always been a feature of the band.
Townshend is also riding high on the success of Lifehouse, the ambitious "play with music" that he has just had successfully premiered on BBC Radio 3. But the real reason might lie in something else Townshend discussed with me: his awareness of the burgeoning Asian market, the coming demand for CDs in India and China which will mean new fortunes for the heroes of rock. As Daltrey said, the music has to be kept alive and in the public consciousness, however much the bones might ache.
These Sixties comeback performers have been joined by Blondie from the Seventies and Boy George from the Eighties in delighting old audiences and occasionally winning new ones. But in every case the return to the stage begs a key question: are the rhythms, posturings, lyrics and social history of rock'n'roll so closely associated with sex, aggression and attitude that a forty or fifty-something performer, male or female, is in danger of looking ridiculous on stage? Perhaps the answer to that is a question in itself: would it not be wrong to preclude artists from performing just because of their age - especially when the public so clearly demands to see them.
Some veterans, though, have found a new way of presenting their songs, one that avoids a traditional rock show with its accompanying expectations of youthful attitude. Steve Harley, founder of Seventies band Cockney Rebel, and Ray Davies of The Kinks, one of the quintessential English singer-songwriters, now do shows with just one accompanying guitarist in which they intersperse their songs with personal histories in the form of witty and sometimes touching monologues.
Bernard Doherty, one of the organisers of both the Q Awards and The Brits, says: "Ray Davies's show had great dignity. It's a great way of not abusing your back catalogue, yet not ignoring it. Contrast that with Diana Ross who seemed to be throwing her back catalogue in because she felt people expected it, and seemed to be doing it through clenched teeth."
The comparison that is often made with jazz is a difficult one. Jazz is part of an older and wider culture. An old jazzman in a smoke-filled room never looks stupid. He would never look like Fifties rocker James Brown did in recent gigs, like Muhammad Ali after one of his last fights.
Rock needs attitude. Twenty years ago, the thought of The Who, The Stones, The Beatles and Tina Turner passing each other on the road, at the turn of the Millennium, would have been laughed out of court. But these days promoters say privately that they cannot find younger bands to put on stadium-style shows. One said: "The likes of Radiohead and Travis keep their heads down and their personalities in the wings."
According to another rock promoter: "Some of the most energetic performers now, like Madonna and Janet Jackson, have tapes playing some of the time so they don't have to sing. When Queen were on stage you had within that act a whole snapshot of 20th-century rock, pantomime, vaudeville. And they loved performing. But when I was at the latest MTV awards one of the roadies told me he was unloading the artists' cases and expecting drum kits and sound equipment, but they were all full of wardrobe and make-up."
So the old troupers will still find an audience, even as they approach the unimaginable age for a British rock star of 60. And those who have comforted themselves with the fact that this could all just be fin de siecle nostalgia, have a shock in store. You think it's all over. It isn't yet. Promoters have been booking stadia around the world for the summer of 2001, when, by coincidence, the Stones will have a new album out.