Muse/The Zutons, Earl's Court, London

How to leap tall buildings and the Seven Seas of Rhye

Nothing exceeds like excess, and nobody does excess quite like Muse. If rock'n'roll is a fantasy playground in which the meek can become giants, and reinvent themselves as Nietzschean supermen, Muse are a band who never know when playtime is over, never hear the toll of teacher's bell.

In his bright red frock coat, looking like a scarlet pimpernel (or, at least, pimp), there's something vaguely Napoleonic about little Matthew Bellamy tonight, and this figures on more than one level. A modest, reserved man offstage, becomes an Empire State Human when he crosses that threshold.

Somewhere between their debut Showbiz and its successor The Origin of Symmetry, Muse made a mental Great Leap Forward. Matt Bellamy, the equally elfin drummer Dominic Howard and the mountainous Chris Wolstenholme (has there ever been a short bassist, in the history of rock?) suddenly stopped seeming like a trio of sixth formers desperately trying to be Radiohead, and they've never looked back.

Aside from one aberrant moment during "Time is Running Out", when Bellamy starts moonwalking while, somewhat incongruously, jackboots are goose-stepping on the big screen above him, Muse are a band with no overt sense of humour. This is entirely in their favour. A sense of humour entails a sense of self-awareness, and self-awareness leads to self-restraint. Muse have none of the internal checks and balances which hold other bands back - if they did, Bellamy wouldn't sing in that falsetto, for starters.

It isn't that Muse are unconscious of the potential ludicrousness of what they do. It's simply that they're mad enough not to care (I often suspect that Muse are, on the quiet, on the same sanity level as a sack of snakes). You can see it when Bellamy holds a showman pose, hammering the strings onto his guitar fretboard with one hand, while fluttering the other aloft like a wizard, amid plumes of smoke reminiscent of those sulphurous chimneys at the bottom of the ocean where weird sock-shaped eyeless creatures thrive. And you can certainly see it when he climbs behind his LED-encrusted piano - it looks like the orgasmatron in Barbarella, or something knocked up by the props department for Doctor Who - for his Phantom of the Opera bit.

Perhaps the most extraordinary aspect of this is the reaction of the audience. Rather than flinch at the muso interludes and wait for the main riff to kick in, they cheer wildly as the camera shows that yes, he really is playing those cascading glissandos on the keys. This crowd loves the craziness: the further out Muse get, the more they are applauded for it.

The giant grape-like pods on the ceiling over our heads are ominous, given Bellamy's theories about alien/human interbreeding (what is he incubating up there?). Looking up at them causes a rush of vertigo, and has you wondering what kind of intrepid men could have scaled such heights to put them there. It's a sensation not dissimilar to contemplating Muse's music: that feeling of awe you get from looking up at tall buildings.

Muse songs are secular magnificats, and as such, they require a leap of faith: is it really OK, you ask yourself, to enjoy music this intricate, baroque and portentous? Then, like the band themselves, you make the jump: yes it is.

No other contemporary band would have the lunatic audacity to mix Mussorgsky, Prokofiev and Bach with Hendrix, Kraftwerk and Queen. (Or at least one side of Queen: if The Darkness have annexed the "Hammer to Fall" half, Muse are all about "Seven Seas of Rhye".) They also, it should be noted, share much in common with all those show-off pomp-metal bands of the late- Seventies/early-Eighties: Rush, Van Halen and co.

They're noticeably un-styled. Bellamy's aforementioned scarlet number probably cost a few quid, but he might just as easily have bought it for a fiver at Scope, with one previous old lady owner. Chris Wolstenholme is clad in a frankly hideous open-necked shirt, black with multicoloured pinstripes, as though he's opened his Christmas presents a week early and is wearing it to please a much-loved, if tasteless auntie. Dominic Howard is wearing loose-fitting khaki shorts, the way drummers do.

There's no unified visual image, no dress code. The message is "don't look at us, listen to us." And if you do need something to stare at, they've shelled out a decent whack on lighting (disorienting flashes of ultra-bright strobes), film effects (a waxing and waning moon cut into strips, that sort of thing), as well as those sinister plumes of smoke.

You don't get any overbearing display of personality from Muse onstage, no clues as to what they're really like. Only what they dream of being. (Which of course is revealing in its own way.) And Muse dream big.

The hazard of dreaming big, of course, is becoming big, and being so popular that your audience can only be accommodated in a draughty exhibition hall, with its popcorn vans and smoothie concessions and Pizza Express franchises. Ideally, Muse would only ever perform in Norman castles, ruined Roman amphitheatres, Gothic cathedrals or Viennese opera houses, using the same PA system as Disaster Area, the heavy metal band from The Hitch Hiker's Guide to the Galaxy.

Instead, they're playing a hall where there's a good 100 yards' empty gap between the last of the standing crowd and the front row of the furthest seating block (for all the atmosphere those poor penned-in souls must be catching, they'd surely be better off at home watching the Hullabaloo DVD). And even in the middle of the auditorium, it's worryingly quiet, unless my ears are finally packing in after 20 years' service to my trade. Until midway through "Ruled By Secrecy", when it suddenly becomes very loud indeed.

Tonight's support act, The Zutons, struggle to fill the void. This quintet of stick figures, knocking out their shit-kicking retro rock, would doubtless like to make Earl's Court feel like the Cavern; instead they make it feel cavernous.

The Zutons, as Scousers so often do, have mouths bigger than their actual achievements (which makes them, effectively, the anti-Muse). Leader David McCabe may speak of his wish to emulate "Sly and the Family Stone or Talking Heads or Devo", or to cross "jazz with funk and soul with country" and create a kind of "voodoo funk", but the reality averages out to nothing nearly so interesting. Their microwaved Merseybeat - or, to be more accurate, Tottenham Sound (they're more Dave Clarke Five than Beatles, and they're feeling thump-thump glad all over) - inspires nostalgia not for 1966 but for 1996. You can just picture them getting thoroughly wasted in the Green Room at TFI Friday with Jo Guest, Paul Gascoigne and a near-death Frankie Howerd. No looking-up-at-tall-buildings sensation with them.

As Muse's set reaches its supercharged synth-rock climax with "Plug in Baby", the pods on the ceiling split apart, and they turn out to be filled with balloons. Black balloons (no concessions to festive frivolity here).

As they bounce in Brownian motion above a sea of batting hands, it's a beautiful sight to watch from afar, like bubbles percolating in a glass of Ribena. It is, at once, sublime and ridiculous. Exactly like Muse themselves.