Yeah Yeah Yeahs, Forum, London; Conor Oberst, ULU, London

'It's not Hallowe'en, you know..." As a recovering goth (goth is like alcoholism, you're never an ex-one), these are words which I, a habitual wearer of black clothing and dramatic make-up, hear frequently in the street, bellowed at me by the delightfully witty citizens of north London.

I never expected to find myself walking into a Yeah Yeah Yeahs gig and muttering the same observation towards Karen O, but these are strange days. Because, as the indie fashion icon bounds onstage wearing a pinstriped business suit (so far, so good), with all the joie de vivre of Clare Grogan circa 1981, she suddenly rips apart her outfit at its Velcro seams, and strips down to a skeleton-patterned backless catsuit, with long tassels straggling down from its sleeves. It's 50 per cent Justin Hawkins, 50 per cent Jarvis Cocker (in his Darren Spooner of Relaxed Muscle persona). After a few minutes, she pulls up the hood, and shrouds her grown-out mullet with multi-coloured tentacles. A few minutes later, she reaches for a plastic bag, and hurls trick-or-treat sweeties into the audience.

Looking around the perplexed expressions this causes the O-clones in the Forum tonight, with their angular black haircuts and Eighties-retro clothes, I can't quite see Karen's latest look catching on in the high streets of Hoxton and Williamsburg.

Not that she isn't still style-conscious - even Yeah Yeah Yeahs' roadies wear fancy Flashdance legwarmers, instead of black tees and builder's bumcrack. But once you've got over the shock of her zombie costume, and her bizarre quasi-aerobic rolling around on the floor (like a New Wave version of Mad Lizzie or the Green Goddess), it does allow the audience to stop scanning her for sartorial tips, and start concentrating on the actual music.

This is rather welcome. Looking back through my previous Yeah Yeah Yeahs review, I can still taste my distaste, a residue of the irritation I felt at the way Karen came across in the media: never seen without a cigarette hanging from her lip, a walking directory of "cool" cliches. This irritation has long since found a new target (Brody Armstrong-Dalle, come on down!), and the YYYs' aural qualities, rather than visual ones, have come to the fore.

This is the Yeah Yeah Yeahs' big comeback, with much new material, and many crowd-pleasers dropped to make way (no "Pin", no "Bang", although we do get "Date With The Night"). In truth, the new songs - characterised by tennis racket-tight punk-funk and flint-sharp New Wave - are indistinguishable from the old.

While this may be an effect of a terrible sound mix in the venue, it is arguably a good thing. Too many bands nowadays don't cement what they're about any more, don't absolutely nail their sound down. And the more I hear the Yeah Yeah Yeahs, the more they impress me. Like The White Stripes, they achieve an extraordinarily powerful sound with just one guitar and one drumkit, and pretty boy Nick Zinner is a remarkable guitarist, almost in the Jack White envelope (there's evidently an affinity: the Stripes covered YYYs' "Maps" at this year's Reading).

As for Karen O, I still find it difficult to dislike anyone who likes Siouxsie Sioux as much as Karen O clearly does, adopting the same consciously flat, hollow howl at any given opportunity.

During the encores, things become curiouser and curiouser. Karen drapes a Virgin Mary cowl over her artificial dreadlocks and begins to scream like a Banshee, while Nick's guitar goes into heavy metal overdrive. Suddenly, this seems to have mutated into a Slipknot gig. I retract all my method-in-their-madness theories above. The Yeah Yeah Yeahs have gone insane.

Bright Eyes. Whether you're male or female, it doesn't matter: as soon as you hear that name, you imagine poor doe-eyed - well, rabbit-eyed - rabbits being menaced by the big black bunny of death. Conor Oberst, however, doesn't carry such evocative associations. But it doesn't matter, because we know that to all intents and purposes, Conor Oberst is Bright Eyes.

Still only 24, Oberst - who shares his home town of Omaha, Nebraska and his record label (but nothing else) with The Faint - released the first Bright Eyes CD at the age of 18, and his precociousness is not the only thing which sets him apart.

As I walk into ULU, he's already onstage, falteringly finding his way through a brand new lyric perched on a wooden lectern. It's a Dylanesque and quite brilliant protest song against Dubya, which ponders "When the President talks to God, I wonder which one plays the bad cop..." and imagines a Bush/deity dialogue in which they decide the fate of the poor ("just give them more liquor stores and dirty coke..."). If you thought - and I know I did - that a thoughtful, intelligent anti-Bush song was impossible in the era of Eminem and Green Day's sledgehammer-subtle slogans, you need to hear this.

It's all utterly traditionalist, but that's OK. Unlike, say, Beck, who smugly parades the trappings of the folk singer, Oberst is a singer-songwriter for whom emotional honesty is the whole point. In his hands, the acoustic guitar - for too long a mere neck-borne symbol, a pendant of affiliation - is an instrument again: an instrument of communication.

Get this. "Although I know my actions cannot be justified, they seem adequate to fill up my time, and if I could scream at myself like I was someone else, maybe I could listen to his advice and not act like such a dickhead all the time." Nudity like this should come with an "18" certificate.

Such self-awareness is, of course, a sign of intelligence, but it also a crippling curse. It will get you nowhere, for example, in terms of sales. Fortunately, he's also blessed. With a wavering, tearjerking voice which constantly makes him sound as though he is being shaken and rattled beyond his control by strange forces, or, if you prefer, like Cat Stevens on spin cycle.

It enables him to hold his devotees - pale, skinny Coxon/Cocker clones in Alfie specs, charity shop jackets and pin badges, and girls who don't have sex on the first date - in the palm of his hand. It's so church-quiet in here that when someone treads on a plastic beer glass, the crunch nearly drowns him out.

Sometimes his desire to be Dylan goes too far. "The sidewalk holds diamonds like a jewellery store case" might be trying too hard, but in the same song ("One Foot in Front of the Other") he redeems himself with "We made love on the living room floor/ With the noise in the background from a televised war..."

Bright Eyes is extraordinary. Burning like fire.

s.price@independent.co.uk