New York guidebooks and jazz magazine polls have been rewritten over the past couple of years, since the music of jazz composer and bassist Charles Mingus has been given a new lease of life. In a small East Village club every Thursday night, the Mingus Big Band redefines the musician's work while raising the roof with its powerful cocktail of blues, gospel, Latin and straight-ahead numbers, all shot through with an infectious exuberance characteristic of its composer. The band is now a fixture on the city's jazz circuit and attracts an eclectic full house to its weekly residency at the Fez club on Lafayette Street.

The term "tribute band" doesn't even come to mind when listening to the 14-piece outfit in action. This is a brash, ballsy band, all brass and reeds plus a kicking rhythm section, that consistently re-interprets Mingus's works. Although the compositions are all Mingus's own, they're played from new arrangements often written by the musicians themselves, resulting in a very contemporary, vibrant sound and a playfulness and energy in its delivery that is infectious.

Charles Mingus died in 1979 aged 56, after succumbing to amyotropic lateral sclerosis (Lou Gehrig's disease). Even after his death he was recalled as a larger-than-life figure, an outstanding bassist and band leader, and an outspoken political activist. But the depth of his compositional skills wasn't appreciated until his major orchestral work, Epitaph, was performed at New York's Lincoln Centre in 1989. The rapturously-received work is now considered the most important long-form composition in jazz since Duke Ellington's 1943 opus, Black, Brown and Beige.

Spurred on by the reception Epitaph received, his widow Sue approached a friend of hers who had just opened the Time Cafe on Lafayette Street to investigate the possibility of setting up a Mingus repertory band. "They had a venue downstairs that they were experimenting with: amateur night, nipple piercings, rock music, poetry readings - all kinds of stuff - and nothing had really caught on," says Sue Mingus. "They had nothing to lose and we had nothing to lose, so we started off with a month contract on Thursday nights and we've been there ever since. There was every reason for it not to work and it just did - it was one of those miracles."

Baritone sax player Ronnie Cuber, who has been with the band since its inception, notes how, with the quality of the musicians in the band, he discovered after a year that some nights he wouldn't even get a solo. "I said `how am I going to stay in the band and stay interested' - I don't want to play parts all night - so I said `I'll write an arrangement and I'll write myself a solo!"

Like everything else about the band, the free-flowing nature of the ensemble means that even those charts that are written for band members aren't set in stone. "Even on my first arrangement - Nostalgia in Times Square - which was only one page long," Cuber says, "the guys in the band added background figures, and it evolved into the likeable piece that we play: a very groovy kind of medium tempo groove." Non-member Sy Johnson, who did arrangements for Mingus himself, continues to be the band's main arranger.

This is tough music to play, with complex changes and rhythms, demanding a lot of input from its musicians. Yet the fluidity and energy that courses through the Mingus Big Band in performance belies the intricacies of the composer's music. Mingus composed over 300 works that span Latin, gospel, blues and cumbia in trio, quartet and orchestral settings, as well as writing a number of pieces for string quartet. Like Ellington and other musicians who had problems with the "jazz" category, preferring instead simply to call what they were playing "music", Mingus strove to break out of the conventions that even jazz can impose on composers and performers, writing pieces that are as fresh and vibrant today as when they were composed 30 and 40 years ago. "He left so much space in the music," says Sue Mingus. "It's very interesting for a composer who wants his music played a certain kind of way to have such faith in his fellow-musicians that he allows that kind of openness. It's structured so that musicians have to come in and play themselves, bringing their own personality and identity into the music."

While the exuberance of Mingus's music is palpable in the five albums the band has recorded since 1993, it's in a live setting that the full complexities and energy of the composer are truly apparent. All the Mingus hallmarks are here: shifting tempos, double, half and stop-time passages, intriguing forms and a whole range of seemingly disjointed elements that all come together in each individual piece. The overall effect is like watching and listening to a flock of rare birds all in unison one moment and then scattered in umpteen different directions the next, emitting differing cries, wails and yells.

`This is different to other big bands, because it has a small-group mentality," says the young Canadian altoist, Seamus Blake, a current band member. "In this band pretty much everyone is a really talented soloist." And that's the real strength of the band - there's never a weak link in the lineup that Sue Mingus handpicks every week.

With such a rich selection of musicians to choose from - over the years Marvin "Smitty" Smith, John Hicks, Kenny Drew Jr, Randy Brecker, Ryan Kisor, Steve Turre, John Handy and Chris Potter have taken the stage, while the current line-up features strong players such as Seamus Blake on alto, the Russian pair of Alex Sipiagin (trumpet) and Boris Kozlov (bass), and the devastating teenager Jonathan Blake on drums - Mingus has no problem filling the band's seats each week. "Everybody who likes the music - and that's most of the musicians that come in - would like to play in the band," she says. "The music is great, the money is good for a big band and we have packed audiences." Mingus also selects the sets primarily because she wants them to play the entire spectrum of Charles's music rather than the pieces which might end up simply showcasing the talents of one or more band members. "When a lot of people think of Charles they think of this raucous, wild music, blues and bebop, and it is all that. But he also wrote very complex, classically-oriented extended works that are incredible and lush ballads."

It's not often one gets to be a bandleader without being a musician, but Mingus has assumed the mantle "by osmosis, by knowing Charles's music and becoming opinionated about it". And it has worked. All of the musicians have strengths in different areas: improvising, reading, and even possessing what Mingus terms "a big personality" like tenorist John Stubblefield, recently described as the band's "resident ambassador of hipness" by current band leader Conrad Herwig.

"Everybody brings something," says Sue, "and maybe some musicians have everything, but because I don't want one personality to take over, I change musical directors all the time. By doing this, by keeping things moving and also unexpected, which is the nature of Charles's music, this very demanding and very structured approach allows - and demands - a certain freedom, spontaneity and unexpected quality."

The Mingus Big Band, at the Everyman Palace Theatre (Cork Jazz Festival), Sunday October 24th. Information: (021)501673.