In Spike Lee's "Mo' Better Blues," Denzel Washington plays Bleek Gilliam, a trumpet virtuoso who has poured his entire life into his horn. When he was a boy and the kids down the block showed up at his front stoop in Brooklyn, ready to play ball, his mother shooed them away and turned the restless youngster back to practicing his scales.

The man who grew up out of this rigorous, sheltered childhood is fully formed as a musician and something less than complete as a person. And this challenge -- of bringing these two aspects of character into balance -- is the crucial one that Lee confronts in this sketchy, invigorating, mystifying film. If in "Do the Right Thing" Lee worked on a broad, social canvas, examining the effects of racism on the culture, in "Mo' Better" he has narrowed the focus to emphasize the personal, examining sex, love and the whole "man-woman thing." And from the look of things, this is not his main area of expertise.

The film, which Lee wrote and directed, divides Bleek's attention between two women, an ambitious would-be singer named Clarke (newcomer Cynda Williams) and a young accountant named Indigo (the director's sister, Joie Lee) who is immersed in show business. Each woman is aware of the other, and both are aware that their major rival is his music. There's a palpable wariness and reserve in Washington's portrayal of Bleek; he's folded in on himself, preoccupied, as if he were constantly tracing the melodies in his head.

Washington gives Bleek a quiet, flashing charm; he delivers a gorgeous, magnetically sexy performance -- a true star performance. There's something bruised about Bleek; his inability to open himself up emotionally isn't merely a matter of macho callousness (though that's how he tries to sell it to the women). Washington makes it clear that Bleek thinks he's saving the best of himself for his art, and that his emotional reticence has a higher purpose. But it's just as clear that the reasons for that reticence go deeper, that fear and pride and inexperience play just as prominent a role.

The threat that women represent to Bleek -- and by extension, to Lee -- is clear. In one scene, Clarke shows up -- as she so often does -- during the time Bleek reserves for practice, then after luring him into the "mo' better" -- Lee says the phrase came from a friend in Washington and means making love -- bites his lip so hard it breaks the skin. In another scene, while he's working up a number, she keeps intruding, and Bleek, in order to keep the flow going, tunes her out.

That scene might not be so offensive if Lee hadn't staged it glibly, for easy comedy. The conflict is real and serious, but Lee seems reluctant to plunge in and deal with it seriously. He seems just as gun-shy as Bleek to explore himself and his emotions.

There are exciting things in "Mo' Better": Bill Lee's orchestral score is lushly evocative (though at times more evocative of a classicist like Copland than of a jazz musician), and cinematographer Ernest Dickerson has given the picture a deep, vibrant, colorful look -- his palette avoids the smoky cliches of the typical jazz film.

Also, the comic exchanges between the actors -- particularly the backstage rapport among the band members -- is hilariously dizzy. Lee can get a thing going with actors, and as a performer himself, he's an engaging comic presence. As Giant, Bleek's longtime friend and manager, Lee's heavy-lidded deadpan saves the character's obsessive self-destructiveness from seeming pathetic. (It's Giant's gambling habit the sparks the film's melodramatic finale.) But the film's only real emotional depth can be found in Washington's performance -- nowhere else. The musical relationships are just as murky as the interpersonal ones.

Lee has said that he was provoked by jazz films like "Bird" and " 'Round Midnight" -- jazz films by white filmmakers -- to make "Mo' Better Blues" and, we're to assume, to get it right. But if Lee was striving to convey a fuller sense of the jazz musician's life, of the connections between black life and black music, or a deeper, more soulful feeling for the music itself, his efforts fall short. From Bleek's music, it's hard to get a grasp on just what kind of jazzman he is. On the face of it, he appears to be a be-bop neo-classicist, in the Branford Marsalis vein. (Marsalis wrote five of film's numbers.) But Bleek hardly seems like the uncompromising, noncommercial avant-gardist that his sax player Shadow (Wesley Snipes) suggests. (For one thing, the club where he plays is packed, though as Bleek says, mostly with white people.)

The real problem, though, is that the only time Bleek's playing has any real fire is when the musical number serves as a backdrop for a vicious beating that Giant gets from a pair of hoods who break bones for his bookie (Ruben Blades). And does Lee really intend to make the facile connection between artistry and pain that he seems to set up?

It's precisely this kind of half-thinking that compromises "Mo' Better" and makes it such a frustrating, partially realized piece of filmmaking. Lee struggles to express his themes -- to assess the price of commitments, both emotional and artistic, to deal with problems of making room for art and a personal life -- but the ideas are so scrambled and inchoate that, unintentionally, the film becomes more a record of his confusion than anything else.

To some extent, the same could be said for "Do the Right Thing." But in that case, at least the choices were emphatically laid out, and if he didn't provide answers at least we were given some sense of the possibilities. Lee's ideas are like broken-off musical phrases, and what the messiness suggests is that he's working too fast, pushing movies into production before they're fully realized, before he knows what he wants to say. This may give his picture a fresh, improvisational feel -- a conceptual heat -- but what is lost exceeds the gain. A jazz piece may be improvised, sketched out in the process of creation, but a movie resists that kind of spontaneity -- or requires skills that are beyond Lee's talents at the moment.

Mo' Better Blues, at area theaters, is rated R and contains some nudity, violence and profane language.