Lester Bowie's Brass Fantasy/Howard Johnson's Gravity Barbican, London
There was a weird moment at the end of last Tuesday's concert when, over the sumptuous closing chords of "If You Don't Know Me By Now", Lester Bowie seemed to will the audience to give him a standing ovation. It was something to do with the way he left the stage and came back, doing his little stiff-backed strut, and his expression of rapture - he really wanted us to adore them.

Not that the magnificent band didn't deserve it, but Bowie's showbiz stagecraft is something you rarely get at a contemporary jazz concert. Take opening band Gravity, for example, led by the mighty Howard Johnson on tubas and tin whistle. Though hampered by a typical-second-on-the-bill mix, their versions of Oliver Nelson's "Stolen Moments", Herbie Hancock's "Tell Me A Bedtime Story" and some expressive blues and gospel-based numbers were a joy.

But where Gravity reinterpret jazz, Brass Fantasy deconstruct. They grab the tradition by the scruff of the neck, pull it apart and reconstruct it in the leader's goateed image. As soon as Bowie, in his customary "mad professor" white coat, had skipped on to stage to ask "Are you ready to rumble?" the band kicked off: a full-throttle brass attack over a raging rhythm section of electric tuba (skinny new recruit David Schieman), drums (Vinnie Johnson) and congas played with sticks (Don Moye). Without keyboards, guitar or bass, Brass Fantasy make a sound hot, dense and wild, with complex arrangements played effortlessly by the remaining line-up of four trumpets, two (instead of the usual three) trombones and French horn - the impressive Vincent Chancey.

The repertoire looks wilfully eccentric: show numbers such as "The Birth of the Blues", camp rock'n'roll such as "The Great Pretender" and "Unchained Melody" and a surprisingly moving version of the Spice Girls' "2 Become 1". Bowie hears these pop numbers as rich, raw material for his baroque fantasies. The most extreme example is "Don't Cry For Me Argentina", a brilliant arrangement that proceeds from abstract gongs and cymbals, through a delicate Gil Evans-ish brass filigree, to tango to rip-roaring stomping funk. Live, much more than on record, it works as a sort of critique of the original Evita showstopper, managing to extract something good, while casting a quizzical ear on the original. The audience's chuckles as they recognised the tune were part of the fun - from this point on Bowie could do no wrong.

Though they are full of the noisy, swaggering bravado and "development noise" that can be tiresome in a conventional big band, in this context they demand your love and affection, your attention and total belief. Why? It must be the way they play them. As Bowie writes on their album Odyssey of Funk and Popular Music (Birdology/Atlantic): "Jazz is neither specific repertoire, nor academic exercise ... but a way of life."

Brass Fantasy have a high level of instrumental virtuosity and stamina and awesome arrangements, but those are to admire rather than love. Bowie adds a personal touch with playing that can be vocalistic and fragile. There's something committed, extreme and charismatic about the way he performs, from the abstract extended cadenza that opens the stomping version of Marilyn Manson's "Beautiful People" to the avant-schmaltz stylings over the closing vamps of the cover of that Harold Melvin and the Bluenotes classic. It's not just music; as Bowie says - it's a way of life.