No,my eyes are not deceiving me. The first of the many occasions those words pass through my head at the Kilburn National is when I spot a cowboy, complete with ten-gallon hat and neckerchief face mask, skilfully abusing the records on the turn-tables in front of him.

As they squawk and quack, and stutter "Lon -Lon -London", three more musicians take the stage, and the sampled beat is drowned out by some glittering disco funk. The drummer, in a white polo neck, looks as if he has stepped out of That Thing You Do!; the guitarist sports a Mafia suit and sunglasses. "Ladies and gentlemen," he announces, "let's have a big welcome for the Best International Male!"

Enter Beck. He stretches up his arms like a triumphal presidential candidate, and the music switches to "Devil's Haircut": a scuffed hip-hop beat, a three-note garage rock bassline, a stack of samples, a country-drawled rap. For a few bars Beck is sliding across the stage, the first person in a decade to attempt robotic dancing; for a few bars he is holding his guitar over his head, while his bassist and guitarist stand frozen on either side of him. He finishes the song by roaring the title with the force of a furnace blast, and then whips out a pair of binoculars "to check out how mah freaks are doing". He scans the audience like an admiral on deck. "Y'all are looking sexy!" he declares.

And so on to the second song of the evening. Space does not permit me to detail all the sparks of genius that illuminate Beck Hansen's show. Suffice it to say that, like O-De-Lay (Geffen), the record that topped so many of 1996's Album of the Year lists, the gig is a painstakingly constructed monument, which somehow manages to give the impression that every brick has fallen into place by happy accident.

Few of Beck's contemporaries compare. The only Brits who can keep up with this Brit-winning Californian's stagecraft are PJ Harvey and Jarvis Cocker - except that while the rest of Pulp skulk in the shadow of their leader, Beck's band join in the fun. And if it all sounds too much like a Las Vegas cabaret, then rest assured that Beck has the ability to appear as if he's not an ordinary person trying to spice up a concert, but a wired individual, acting in a way that he considers normal. When he involves the audience in some call-and-response (Beck-and-call, as it were), the ritual is no longer the patronising standby of every rap gig and stadium- rock show, but is galvanised by his bug-eyed, evangelical urgency. If the crowd doesn't comply, it seems, the singer will spontaneously combust. Now that's star quality.

Another defence against the charge of the show's being gimmick-reliant is that Beck doesn't even need two turntables and a microphone to entertain an audience: in the middle of the overdriven, jumbled barrage, there is an oasis of Dylanish acoustic songs. Thanks to Oasis, of course, unplugged sets have become cliches themselves. Not in this case. For half of Beck's unplugged set he does without even a guitar, and instead blows a train- a-comin' blues harmonica to the rhythm of the audience's applause - as long as we keep in time. "Damn, y'all are too fast!" he yells, when excitement gets the better of us. "Y'all been listenin' to too much Jungle! A man cannot play the blues that fast!"

A cutting-edge artist who gets back to the roots of country, folk and blues, Beck is not just the future of music, but the past as well. How on earth did he win a Brit Award?

To dispense with the puns straight away, Reef's show at the London Forum on Monday wasn't quite as great, and it didn't break down any barriers. The West Country quartet, augmented by a pianist, bounded through their familiar brand of rugged, brawny, ruddy, hearty, hairy-chested, firm-jawed, stoneground, high-fibre, All-Bran blues-rock; and Gary Stringer let loose his raw-throated son-of-Paul-Rodgers-and-favourite-nephew-of-Mick-Jagger vocals. Reef are Ocean Colour Scene with the pretension swapped for leonine sex appeal.

The band sound more confident on their second album, Glow (Sony), but otherwise they haven't changed since its predecessor came out in 1994 (their music hasn't changed, one could add, since 1971). Their apologists point out that these albums are more diverse than their singles might suggest, and it's true: sometimes, the feelgood hard-rock anthems make way for lyricless, repetitive, improvised odysseys. These are, however, the low points of the evening. Be warned, Reef: keep it punchy and hooky. One band of Black Crowes is enough. More than enough, in fact.

To conclude our survey of pop artistes with four-letter names, we come to Lamb. They sound utterly unlike the other two - their music is characterised by Louise Rhodes's sliding, snaky vocals and Andy Barlow's teeth-rattling break beats, a bit like hearing a lullaby in one ear and an alarm clock in the other. But their show at the London Astoria on Wednesday did have something in common with Beck's. One of their crack team of additional musicians played a guitar with a violin bow. Could this be the first sign of a Jimmy Page revival?

What then are we to make of the other instruments that ebb and flow through Lamb's spellbinding music? The fluttering trumpet and double bass were more jazz than jungle; the string section belonged to the soundtrack of a cold-war thriller; Barlow stopped bouncing around behind his keyboards long enough to hit a bongo; and on one song Rhodes accompanied her truly, madly, deeply romantic lyrics with a few plucks of the zither.

In short, Lamb are just about uncategorisable. Sometimes, they can sound like Morcheeba or Moloko, and they have more in common with Bjork than with anyone else, not least because Ms Rhodes and Ms Gudmundsdttir evidently go to the same eccentric tailor. But none of these comparisons is quite accurate. Cloning a sheep is all very well, but finding another band like Lamb is a real challenge.