The Seattle trio's rapid rise from obscure Pacific north-western noise-makers to worldwide pop sensation in the Michael Jackson league, has been based on the excellence of their music, but this fact has been rather lost in the media frenzy that has surrounded them over the past couple of months. The band's singer and guitarist, narcoleptic genius Kurt Cobain, is a fascinating figure in his own right, but the suggestion that his career may have been hijacked by his wife Courtney Love, the scheming, Nancy Spungen-fixated lead singer with visceral shock-rockers Hole, sent speculation spiralling in new directions. Had she got Kurt hooked on heroin in the early stages of her pregnancy? Was she, as she claimed, smoking a lot to guarantee herself a small baby?
The suspicion that an element of misogyny may be creeping into the atmosphere is supported by events at Reading, where, earlier in the afternoon, feisty Los Angeles rock'n'rollers L7 get pelted with mud, apparently for the crime of not being men. It can't be for any failings in their music, as they perform a blistering set of infectious political punk-metal. Eventually the thuggish minority prompts them to drastic action. After a few moments of conspiratorial shuffling about onstage, lead singer Donita Sparks responds with a missile of her own, swinging it round her head before confirming the fears of the more delicate members of the audience: 'Eat my used tampon,' she shouts spiritedly. The really frightening thing is, someone throws it back.
Nirvana's friends and former label mates Mudhoney live up, like them, to the Nineties grunge-pop ideal (which means cranked-up Sixties garage fuzz, mixed with Seventies metal power and punk attitude, and belted out through a deceptive mask of Eighties apathy); but unlike them, they don't quite transcend it. They lack the spark of charisma that makes Cobain and Co - currently backstage trying to hide from Radio 1's Jakki Brambles - special.
When Nirvana finally come on, bassist Chris Novoselic says something about how he can hardly bear to see such suffering, and Kurt is wheeled out in a hospital chair, wearing a white house-coat and a big, blond Courtney wig. With agonising slowness he pulls himself out of his seat, reaches for the microphone, sings a line from U2's 'One', then dramatically falls to the ground. This may not sound funny, but the effect on 40,000 rumour-lashed, rain-sodden souls when he bounces back up again is a delight to behold.
Any carpers are confounded by a crisp, ferocious set not hugely different from their ground-breaking show here last year, except that the material from their Bleach and Nevermind albums now seems like a non-stop greatest hits selection. Their sound may be heavy, but it is never sluggish, and there is a real poetic quality to Cobain's voice on songs like 'Drain You'. There are also a couple of fine new numbers, a further hopeful sign that rumours of the band's imminent demise could well be exaggerated. And a song is even dedicated to his healthy 12-day-old daughter, Frances Bean.
In the swankier surroundings of the Royal Festival Hall, another great American performer totters on to the stage with a deceptive show of incapacity. Sandra Bernhard begins her show 'Giving Till it Hurts' in the guise of a zonked-out hotel lounge smoulderer. When she eventually finds the microphone, she and her fine two-man/two-woman band, The Strap-Ons, wrap themselves languorously around Peggy Lee's much abused 'Fever', and squeeze life back into it. The words are changed - 'A lot of people are confused by my sexual ambiguity, but honey, not as much as me' - but the spirit is real, undimmed by jokey asides about Ms Lee's wig.
With the exception of a savage assault on Madonna's 'Justify My Love', Bernhard's musical numbers are not parodies. She has impeccable taste - her material ranges from Prince's 'Litte Red Corvette' to Aerosmith's 'Dude Looks Like a Lady' via Streisand's 'People' - and sings a lot better than her detractors would have you believe, in a voice that is sure and occasionally almost operatic. As well as being very entertaining, the songs serve as pegs around which she weaves a series of skilfully observed monologues and character studies (written in tandem with low-profile collaborator John Boskovitch), usually at least partly autobiographical, but all with a wider significance.
Cat Stevens's 'Sad Lisa' is a cue for reminiscences about Sandra's high school role model, who disappeared into the desert, and a meditation on freedom of expression. 'Mighty Real', Sylvester's great gay disco anthem, makes a pulsating soundtrack for the saga of Sandra's bisexual awakening, which is also a reflection on the changing meaning of San Francisco. She is outrageous, getting changed onstage and exulting in her dirty mouth, but she is also a serious cultural critic. When Bernhard says that Jacqueline Susann (author of key Bernhard text The Valley of the Dolls, whose film theme she performs with great feeling) 'lived a Sixties Oliver Stone never even dreamed about', or that fashion designer Karl Lagerfeld 'has healed the wounds between rich and poor', her industrial-strength irony is beautifully directed.
The only British comedian who comes close to Sandra in terms of icon literacy is (at his best) Vic Reeves, whose appeal can be similarly bewildering. Unlike the fop Reeves, her act has a heart and a point, the mix of glitz, satire and melodrama firmly focused on the ideal of a less hung-up world.
Those whose only exposure to Bernhard has been to see her disdainfully swatting aside the questions of hostile and uncomprehending TV interviewers over the past few weeks could have been forgiven for wondering what all the fuss was about. But only a true churl could fail to be dazzled by her in person.