The opening note of Jazz, Ken Burns' new 10-part series for PBS, comes from trumpeter Wynton Marsalis, who's not playing but lecturing. "Jazz music objectifies America," he tells us, then offers a lesson about what jazz really is. The form's great power emerges from musicians who "negotiate their agendas with each other." According to Marsalis (he's Lincon Center's artistic director for jazz), that negotiation, that handing off and passing around of inspiration - that jam - is jazz's transcendence.

Most jazz musicians would agree. As the clich´┐Ż goes, it's one thing to do a show for your paying customers, playing what they expect and have paid to hear, but after the squares go home, you can stop blowing shit and make another kind of music altogether. Yet many musicians would also agree that, more often than not, it's a lot more satisfying to play that personal kind of music than it is to sit and listen to it. Jazz musicians involved with each other in intimate creativity may well be negotiating their way to improvisational sublimity, but they've often left the audience out of the musical deal. This is a central but rarely acknowledged tension in Burns' documentary treatment.

Neither Burns nor PBS would be presenting nearly 19 hours of archival footage and contemporary performances and interviews unless the series could claim, as it does repeatedly, that jazz is a fundamentally American art form that reveals much about the culture from which it has sprung. But it would reveal nothing if jazz had not been a commercial form to begin with, if - to put it in Marsalis' terms - its original makers had not hungrily included the customers in the negotiation. For all its knowing (and legitimate) commentary about expressive artistry, for all the context of romantic creation, Burns' film actually works best when it showcases jazz as an opportunity for its audience's ecstatic pleasure.

Albert Murray, one of American culture's greatest critics (because his work is broadly instructive, rather than narrowly judgmental), puts the matter directly in one of his appearances. Playing a contrapuntal riff to Marsalis' Professor of Negotiation Studies, Murray says simply, "Jazz is dance music." That doesn't mean jazz isn't also a lot of other things. But it does mean that jazz's artistry is deeply rooted in sensual pleasure. The farther jazz has strayed from those roots, away from breathless, sweat-beaded ecstasy, the more clubs have closed, the more radio stations have switched programming (often to its rhythm-and-blues-based offspring), and the nearer it has approached its appointment with public broadcasting. PBS has fallen into the role of cultural memorializer, the celebrator of dead genres.

Yet Burns' series, its self-conscious gestures toward epic notwithstanding, is filled with rewards, many of them proffered unintentionally. Jazz is indeed an American story, which means that art and commerce need not be separate and opposing forces. Indeed, the former triumphed through the latter, rising from whorehouse scorn in such places as New Orleans and Kansas City to find an enthusiastic audience despite the original dismissal of gatekeeper critics (Gilbert Seldes notably excepted), editorialists, and even doctors, before eventually falling into the suffocating embrace of Lincoln Center itself.

Burns doesn't set out to tell that tale, but that's the story that emerges, over and over again. Burns' documentary gifts are not visionary, analytical, nor even properly historical. Rather, he is a talented biographer, and his films are most effective when he is able to present an overarching narrative in terms of the biographical detail of that narrative's participants. The approach worked especially well in his Civil War series, because it unexpectedly humanized the war. It didn't work so well in his baseball series, because the mass of detail tended to obscure the game itself; few sports fans really want to know their heroes out of uniform.

But as Vasari might have told Burns, biography - even when it's legend - is a good way into culture. Thus we have a century's worth of the lives of the jazzmen and women, told sequentially and profusely illustrated. (The rap against Burns is that he has left some important people out of his group portrait, a charge he invites by claiming epic comprehensiveness.)

What has Burns revealed? Given 19 hours in praise of every kind of jazz, viewers will be able to take away every kind of moral. But one lesson that seems hard to ignore is that jazz was at its strongest when its makers embraced their audience and used their popularity to develop the audience musically, even leaving themselves open to learning something from that audience. Anybody can play the contemptuous bohemian, a type that was eventually to overwhelm the world of ever-more isolated jazz makers. The real artistic work lies in forging a connection with the audience, inviting it to share in the innovation. That's actually a rhetorical skill as much as it is a musical one, and is on display in every frame Burns includes of Louis Armstrong. Armstrong was as immensely influential as he was not only because he was a great trumpet player, but because he embraced his audience, was anxious that it enjoyed itself, and was thus able to take it with him, note by soaring note.

Perhaps the most instructive sequence in Burns' series involves Armstrong's character opposite, Duke Ellington. Ellington's whole career was built on a remarkable marriage of jazz , elegance, and dignity (traits embodying the cultural longings of Ellington's black Washington, D.C. milieu). Yet in 1956, with jazz receding into elitist taste and his own career in the balance, Ellington jump-started his creative life by nearly starting a riot at the Newport Jazz Festival. Characteristically, Ellington had composed a long, serious suite for the occasion. But when he saw his audience heading early for the parking lot, he broke the band into "Diminuendo and Crescendo in Blue," a hard-driving work he'd written in 1937. The crowd turned back. Famously, one beautiful woman started to dance, and the crowd gathered around her. Ellington dug into the number, even when the worried festival impresario signaled for him to cut it off before the usually polite Newporters got violent. Saxophonist Paul Gonsalves did 27 choruses, and the band followed with four encores. "I was born at Newport," Ellington liked to say afterward.

There's also a cautionary tale for this theme of audience embrace: the career of Miles Davis. Davis had enjoyed success as a musician of aloof cool, but started to chafe when pop groups like Chicago used his riffs to get very rich. Davis actually asked his label to stop calling him a jazz player at all, having concluded that it was a barrier to reaching a larger audience and making real money. He eventually was to find that audience, at least for a while, by playing the rock-jazz mix known as fusion. But many people agree that this was a dead end for both Davis and his listeners.

Why? The answer again has to do with the issue of musical negotiation. Davis' musical identity was originally built on artistic distance, on insisting that the audience come to his music. But when he switched strategies and went in search of a larger audience, he made the (perhaps inevitable) mistake of staying aloof: He never learned how to teach his new audience what he wanted it to appreciate, or for that matter to learn from it either. In the albums that follow 1969's Bitches Brew, Davis doesn't seem to know what he wants to play. Sustained success is not just about a happy, buying audience. It's an ongoing dialogue - a negotiation.

The same is true for many other forms, of course. But jazz's lesson is especially valuable because, for one thing, its compressed history is a fractal of these other cultural histories, and for another, that history is suffused with unmitigated pleasure. Burns gives his audience 19 hours of that history, a lot of time for a lot of extraordinary people to play and find (posthumously, in many cases) another generation of admirers to talk with.

Never mind the lectures: What a concert.