The Critics: Rock & Pop: The prat in the hat is back

Jamiroquai Brighton Centre, Brighton Sebadoh Shepherd's Bush Empire, London

Jamiroquai seem to be almost fashionable again. Years after we'd written off Jason Kay as that dope-smoking, sports car-driving, funny- hat-loving Stevie Wonder impersonator, he's suddenly winning awards, grinning from magazine covers, and generally being taken a lot more seriously than a man who wears wombats on his head has any right to expect. One reason for this rehabilitation is that he is now one half of a celebrity couple, the other half being Denise Van Outen. Kay's ramblings on the state of the world have earned him almost as much ridicule as his taste in millinery since his first album came out in 1993, so we shouldn't underestimate the if-the-People's-Totty-fancies-him-he-can't-be-that-much-of-a-ponce factor. But even more significant is the sheer number of records Jamiroquai have sold. It's not so easy to dismiss them as an acid-jazz irrelevance now they've shifted 11 million albums.

Their fourth and best LP, Synkronized (Sony), is released tomorrow. To mark the occasion, a UK tour began on Wednesday, staged on a scale befitting Kay's new superstar status. There were video screens, a giant illuminated globe, a whole solar system of mirror balls and a metal climbing frame behind the nine-piece band. Otherwise it was funky business as usual. Kay boogied with an unselfconsciousness that no other male Caucasian can summon unless he is safely in his kitchen; and he wore two different hats (and you don't often hear that said literally). One was of his usual style, ie, a palace guard's bearskin that had been sat on. The other was a feathered head-dress that could have been attached to a handle and used to fan an Egyptian princess.

Chapeaux aside, Kay comes across as gracious and down-to-earth. He made one too many references to Van Outen, but he was remarkably sincere in his appreciation of the audience - the "party people" - and of his new bassist, Nick Fyffe. Fyffe was apparently recruited from a Jamiroquai tribute band after his predecessor, Stuart Zender, left the band to spend more time with Mel Blatt of All Saints.

When Kay had to restart "Virtual Insanity" after fluffing the lyrics, the audience's energy doubled. This was in part because of the singer's good-natured self-deprecation, but also because it was the first unplanned and unexpected moment of the concert. Kay likes his music the way he likes his Ferraris: precision-engineered. Every note is in place, every arrangement has been pieced together beat by beat. And to an extent, this is to be admired. You have to take your furry hat off to an artist who knows exactly how he wants to sound, and there are few bands that are so well-drilled.

The danger is that all the danger is removed. For every great single on a Jamiroquai album, there are several tracks that you don't have to listen to because you know what they sound like already: generic jazz- funk disco, a background hiss of rickety-tickety hi-hat, complicated electric piano chords, scurrying bass and scattish vocals. It's a shame there aren't a couple more songs that catch you unawares, as, for example, the buzzing keyboard bassline on "Deeper Underground" does. On Synkronized, the other obvious examples are the rattling scrape of a detuned guitar on "Supersonic" and the Baroque piano twiddles on "King For a Day". Neither track was played on Wednesday.

The other problem is that Kay's slip-sliding voice is as frictionless as his dancing. The group's next single, "Black Capricorn Day", is about being depressed, but Kay's vocals on it are as sunny as when he sings about being a famous TV presenter's boyfriend. (And given the criticism that is most often levelled at him and his music, it must take some courage to sing the refrain, "It's much too black for me" over and over again.) Jamiroquai are masterly at what they do, but half the time what they do has been done before. If you're looking for guts and daring during the other half of a very long concert, well, that's what the hats are for.

Opening their show last Sunday with a song about "pretending you're bigger than you really are", Sebadoh went on to pretend they're smaller than they really are. The Massachusetts trio's latest album, The Sebadoh (Domino), is stuffed with heartfelt lyrics, haunting melodies and fearsome riffs. It's even yielded a top 40 single and a Top of the Pops appearance. But Sebadoh still set up their own equipment before they start playing, still stand in the middle of a stage that is bare but for the guitar-cases stacked by the back curtain. "This is a very big stage, Jason is very far away," worries Lou Barlow. There are all of two metres between him and his co-frontman, Jason Lowenstein.

Sebadoh don't look like rock stars. The lank-haired Lowenstein could shed a few pounds, and when Barlow brushes back his curtain of hair he reveals the face and glasses of Louis "Weird Weekends" Theroux. But what really holds Sebadoh back from fame and fortune is their own distaste for such trifles. The height of their ambition is to be nothing more than grungey slackers in the early-Nineties mould of Buffalo Tom, the Lemonheads or Barlow's previous band, Dinosaur Jr.

Sebadoh do, however, sound like rock stars ... or they could do with a few minor alterations. In concert, Barlow's sensitive, folk-influenced songs and bruised voice made more of an impression than Lowenstein's throat- damaging,head-banging work-outs. But both men could be on Top of the Pops as often as they liked if Sebadoh allowed someone to clean up their muddy production and tune their guitars. I can't decide whether their determination not to be REM is noble or just annoying.

Jamiroquai: Hull Arena (01482 325252), Mon; Newcastle Arena (0191 401 8000), Wed; Glasgow SECC (0141 248 9999), Thurs; Wembley Arena (0181 900 1234), Sat & Sun