ROCK: It's tiring work, being Bjork

When A musician inspires a certain level of devotion, the standard response from critics goes like this: "Artist X could play her greatest hits on xylophone and penny whistle, with backing vocals from a herd of Fresians, and the fans would still love it." But only in the case of Bjork is there any likelihood of this hypothesis being tested. As anyone who has ever seen her in concert will know, her live arrangements never have more than a passing resemblance to those on the records. The big-band extravaganza of "It's Oh So Quiet" on castanets? "Venus as a Boy" on wooden spoon and kettle? Why not?

So Wednesday's show at the Shepherd's Bush Empire was somewhat unnerving. Bjork has summed up her latest album, Homogenic (One Little Indian), as "beats, voice and strings", and yet, behind her sat what looked suspiciously like a string octet, and separated from them by a perspex screen was Mark Bell, whose job was to trigger his spitting, spluttering, crackling beats. Add Bjork's peerless vocals to the equation and you have what can only be described as beats, voice and strings. Just like on the album. This made for one of Bjork's most accessible concerts in recent years, but also one of her most disappointing.

This judgement should be understood only in the context of Bjork's stratospheric standards: any sensible discussion of her work has to begin with the premiss that she is arguably the most important individual in contemporary pop. There is no one else who has that incredible, atomic voice. There is no one else who could match such a voice with a fiercely individual personality, or who could take their music to uncharted territories, while never straying far from heartfelt lyrics and beautiful, chartbound melodies. On her worst day Bjork is a mesmeric performer, bursting with ideas and radiating her own hyperactive-child charisma. Of course, it doesn't do her any harm that she is one of the decade's most striking and influential fashion icons: in the next few months, watch out for clubbers wearing skirts under pink dresses that are backless from the waist down, and expect elaborate hairdos to be replaced by just-got-out-the-shower flops.

But being a genius is hard work, and on Wednesday Bjork seemed in need of a good night's rest. Again, this is true only when measured on a Bjorkian scale. She is still more mobile than all four members of Cast fired out of a cannon, and it does seem cruel to call her subdued after she yelled her head off at the end of "Pluto", while Bell made gunshots and cracking ice explode around her. But instead of scurrying across the stage like a frightened mouse, as is her wont, Bjork confined her movements to some riding-along-on-the-crest-of-a-wave hand-jiving, and a few hops, skips and jumps. She didn't play "It's Oh So Quiet".

Maybe she scaled down her movements to fit the venue, which was much smaller than those she filled on her last tour. This being the case, there was a surprising lack of connection between Bjork and the audience. She sang some of her songs with a drooping head and with her eyes closed, and she didn't say anything except the occasional "sank you".

It was up to us to peer into her world. And on Wednesday, her world was the mermaids' grotto in a local production of Peter Pan. Above her head were tangles of wire and swathes of polythene, and behind her were wispy streamers, lit by blue and green swirls. Any setting that evokes Peter Pan may seem appropriate, given Bjork's woman-child image, but this week it seemed that, at 31, she may be slowing down, very slightly, with age.

On the subject of unsuitable settings, what were Jonathan Fire Eater doing in the Union Chapel on Tuesday? There may be something perversely apposite in seeing such an unholy band there, but London's most tranquil and atmospheric rock venue is a haven for subtle acoustic sounds, and JFE make ramshackle garage rock'n'roll to stamp your Cuban-heeled boots to, not to appreciate quietly from a haemmorhoid- inducingly cold pew. For a band who were initially pigeonholed as goths - their first EP, Tremble Under Boom Lights, spun tales from the same crypt as Gallon Drunk and Nick Cave - JFE are shockingly good fun, and Wolf Songs For Lambs (Deceptive), is possibly the most fun album of the year. Be warned, though: I say this as someone for whom the JFE formula - Iggy Pop fronting the Modern Lovers, with some production tweaks from Beck - is not far from a dream come true.

Wednesday's show began with the anvil clang of a two-note guitar riff ringing from the darkness. The lights came up on a band with matching short haircuts and with white shirt-collars sticking up over black jumpers: it's possible they haven't changed clothes since they first met as schoolboys in Washington DC. Stewart Lupton ran onstage, hurled a bunch of flowers into the audience, and then spent the next half-hour trying to wriggle out of his tight, stripey jersey. A graduate of the Mr Bean School of Choreography, Lupton aims for Jarvis Cocker's so-uncool-he's-cool trick, but founders around so-uncool-he's-odd, alongside JFE's closest British relatives, Tiger. "I feel pretty good, I feel all right," he yelped between songs, but looked so peaky that you expected him to be led gently offstage by a nurse at any moment.

The band were in robust health, though. Their splendid racket is a pile- up of Matt Barrick's fat, thumping "Wipe Out" drums, Paul Maroon's loose guitar, and a blaring, fuzzy, saw-toothed organ noise, the like of which can be heard on the Smash Mouth single, "Walkin' on the Sun", and, to get trainspotterish about it, on Elvis Costello's "Pump It Up" and the Modern Lovers' "Roadrunner".

It's the overall sound of the organ that is sublime, rather than the intricacies of Walter Martin's playing, and the same could be said for the JFE live experience as a whole. There was almost no change of pace or style, so that the short set could have been one long, incessant song, with a pause every three minutes for Lupton to croak, "Thank you, allelujah." These were more or less his only coherent utterings of the evening. My companion (as a restaurant reviewer would say) was able to make out the words "747", "motel" and another which is unprintable. That was two more than I could swear to.

Three years ago I went to a concert which was, I hope, the closest to Altamont I'll ever see: football-crowd chanting, people clambering on stage, security guards grappling them off, the singer being pulled into the audience, security guards diving after him. Somebody even tried to steal the wobble board.

Thursday's Rolf Harris gig at Dingwalls in Camden was a little less riotous, and a little more straightforwardly joyful. Who knows, though, if he appreciates the tone of the audience's adoration? There was no doubting the sincerity of their love, but this was mixed with a frenzied studenty irony, which didn't stop him delivering Australian history lessons, rather than relying on the easy option of pure self-parody. Theorising aside, you have to admire someone whose band can make the works of the Kinks, Lou Reed, Edwyn Collins and Alanis Morissette sound like his own compositions. How could we ever have thought that "One Hand In My Pocket" was complete without the world's nicest sexagenarian's didgeridoo?