Rejoice! rejoice! A no-encore gig! Paul Draper pushed his guitar up against an amp, the noise buckled and crashed ... and that was it. Mansun had left the building, and Abba's "Dancing Queen" was already blaring from the PA. Excellent. I know that not everybody shares my loathing of the cliched, insincere "encore" ritual, when the singer bids us goodnight knowing full well he's going to reappear two minutes later. But I also know that encores are so pervasive that when a group doesn't do them, it merits a mention. Besides, the last young bands I saw who skipped the insulting formality were Suede and Oasis. Is Mansun's omission an intimation of similar greatness? In their own minds, definitely.

Mansun have put on the eyeliner, pulled out the stops, and gone for this rock-star business in a big way. Their chart-topping debut, Attack of the Grey Lantern (Parlophone), was produced by Draper, and one can imagine him pressing every button in the studio, plugging in every instrument, blowing the dust off old machines and demanding to know what they can do. He has given Grey Lantern a "concept". He has shoved in some dance beats and some strings. He has thrown in some Blur (music-hall melodies and lyrics about transvestite vicars), some Oasis ("She Makes My Nose Bleed" is showered with "Supersonic"'s molten guitar) and some Suede (the glam posturing of "Mansun's Only Love Song"), to name but a few of the nearly-epic album's ingredients.

Similar admirable delusions of grandeur distinguished Mansun's show at the Cambridge Junction last Sunday. No encore (terrific move). No banter. Five full instrumental minutes before the vocals come in. One song segueing into another until, after two or three songs, there is a final chord that lasts 20 drum-rolling, guitar-twiddling seconds. Sometimes you have to risk being laughable (Mansun's attitude seems to be) if you want to make your mark.

Their clothes are proof of this. Sunday's military coats and carefully arranged safety pins - a designer punk look that Duran Duran might have sported 14 years ago - are the only outfits imaginable that could have made me long for the return of the orange boiler suits they used to wear.

But is there any substance behind Mansun's dramatic flair? Well, sort of. The poodle-haired Dominic Chad plays a nicely off-kilter lead guitar, and Draper, who tonight resembles a baleful Damon Albarn, has written a few cracking songs. None the less, one is left emotionally uninvolved, with the hollow feeling that Mansun are a manufactured band, even if they've manufactured themselves. One reason they change their style so often may be that even they haven't decided how they want to sound.

The eponymous leader of the Ben Folds Five has as much musical and literary talent as any American songwriter working in rock today. The question, though, is whether rock is what he should be working in. His songs are showtunes with swear-words. Bitter and incisive Whatever and Ever Amen (Sony) may be, but you can't hear the fresh, sunny melodies without expecting a girl in tap shoes to chirp: "Let's do the show right here!"

Alongside the dynamics and modulations and time signature changes, what makes Folds's music so ripe for an off-Broadway chorus line is that there's not a guitar in sight. At the London Astoria, Folds - the spirit of Randy Newman in the body of Rick Moranis - plays the piano. Not just the odd bit of boogie-woogie, but full, ten-fingered chords and fiddly singer-songwriter arrangements. His two colleagues - the line- up of the "Five" is Ben Folds (vocals), Robert Sledge (bass), Ben Folds (piano), Darren Jesse (drums) and Ben Folds (songs) - battle on gamely, Sledge racing up and down the fretboard, Jesse furnishing "Steven's Last Night in Town" with a "Lust for Life"-style voodoo beat on the toms. But they're almost redundant. Their leader plays as if he were in the Ben Folds One.

As the principal effect of the band is to make the smart, smarting lyrics almost impossible to hear, what is the point of playing such sophisticated songs in this context? Well, Folds seems to enjoy pretending to be a punk. On "Steven's Last Night", again, he tootles on a melodica, and then plays a piano solo by whacking the ivories with a microphone. He mentions the Spice Girls - a reference which has superseded last year's "So, you guys have mad cows, huh?" as every visiting American rock dignitary's attempt at local humour. But these are all brief interludes, wedged in between longueurs when Folds crouches over his baby grand and doesn't acknowledge the fans at all. They resort to amusing themselves by crowd-surfing, turning his compositions into music-to-be-passed-over-people's-heads-to. The songs deserve better.

Pavement don't quite deserve the praise that British critics - and Blur - heap upon them, but there's no denying the perverse prettiness of such songs as "Shady Lane", the next single from Brighten the Corners (Domino). The droning basslines drag along the floor - the bass has Fender Precision stencilled on it, which seems something of a misnomer; distorted chords fight with a dissonant lead guitar; and Steven Malkmus, or whichever other member is taking his turn at lead vocals, talks, croaks or squawks like an injured seagull.

And yes, for all that, the music is still pretty. Close your eyes and you can imagine the Pixies, or, at other times, Lou Reed. Open them, and there onstage are the four finalists of a Jeff Daniels lookalike contest, plus a bearded drummer who must be the president of his local ramblers association.

At the Portsmouth Pyramids Centre on Wednesday, the artpunk nerds were almost as shambolic as they're reputed to be, punctuating their show with running-order debates, and grinning admissions of, "Whoops, not supposed to sing yet." Still, much to my surprise, I'd recommend seeing them, just to laugh with - not at - their deliberate amateurism for half an hour or so, before it starts to grate. You have to give them their due. When Americans impersonate the Pixies, they end up with Nirvana and Pavement. When Brits do it, we end up with Bush.

Mansun: Bristol Bierkeller (0117 9268514), Mon; Brighton East Wing Centre (01273 202881), Tues; Exeter Lemongrove (01392 75016), Wed.