What’s he hiding? That question nags at you when you’re around Ken Burns, precisely because he seems so willing to show you and tell you everything. Come on up to his headquarters in Walpole, N.H. Be a fly on the wall when he’s working, in the old house he’s used for the editing and production of such PBS documentaries as “Lewis and Clark,” “Thomas Jefferson” and–the reason you’re here–his 17 1/2-hour epic “Jazz,” which begins airing on Jan. 8. Take notes on the pop-funky decor. (Ready? Photos of Miles Davis and John Coltrane; an action figure of the Incredible Hulk grasping a Teletubby; a figurine of the Big Boy; a photo of Mark Twain in drag, kicking up a leg.) Then on up to his house outside of town for a sit-down interview. First you meet his two golden retrievers (“Jackson is the GREATEST, SWEETEST, SMARTEST dog. Now, lie down. No, all the way”). Then he exhibits, with a sort of besieged complacency, his long schedule of phone interviews for the day (“So this is a day when I’m resting at home”). And then he brings up, unprompted, the most painful subject on your (and his) agenda: the early death of his mother, which, by his reckoning, determined both his life and his life’s work. By the time you’re back on I-91, you’re pretty well convinced Burns isn’t hiding much–that showing and telling, in fact, is his life. But that doesn’t mean there’s no mystery there.

Burns’s 10-part “Jazz” is the longest of the 18 films he’s made in the past 20 years, and he believes it’s the best. He calls it the third part of a trilogy that includes “The Civil War” (1990) and “Baseball” (1994), each seen by at least 40 million viewers–although, true to his improvisational method of working, he’d never planned any such thing. “So I’m in the middle of making ‘Baseball’,” Burns recalls, “and I have this interview with [essayist] Gerald Early. Early says, ‘When they come to study our American civilization 2,000 years from now, we’ll be known for three things: the Constitution, baseball and jazz music. They’re the three most beautiful things Americans have ever produced.’ And it hit me right in the head. The Civil War was the Constitution’s greatest test. I’m in the middle of ‘Baseball.’ Jazz, maybe?”

If this seems like an incongruous assortment of subjects, Burns points out that the theme connecting his three films is race–“Baseball’s” principal iconic figure is Jackie Robinson, not Babe Ruth or Joe DiMaggio–and that his America is a multiethnic, multiracial “gumbo.” “My rap has been, ad nauseam, that we put African-American history in the coldest and shortest month–February–as if it’s some addendum to American history,” he says. “And it’s actually at the center. And you just gotta get over it.” And jazz, according to Burns, is at the center of American culture. “It’s the pie-in-the-face irony of all time that these people, who’ve had the experience of being unfree in a free land, created the only art form Americans have made. If you want to know about your country, you gotta know about this music.”

Burns’s outline of jazz history will surprise no one: from New Orleans (Jan. 8) to Chicago, New York and the world; from Louis Armstrong to Duke Ellington (Jan. 9, 10 and 15) to Benny Goodman and the Swing Era (Jan. 17 and 22) to the bebop insurgency of Charlie Parker and Dizzy Gillespie in the 1940s (Jan. 23 and 24) to the avant-gardism of Coltrane and Ornette Coleman in the late ’50s and early ’60s (Jan. 29) to… well, to 40 more years in which our sense of a forward-marching history has petered out into a mishmosh of jazz-rock fusion, post-avant-gardism and neoclassicism, and which Burns crams into his 10th and final episode (Jan. 31). “I just unhitched my narrative,” he says. “I refused to tell the present what it’s about.” And Armstrong, rightly, is the central figure. “My own anxieties about mortality are tempered just slightly,” says Burns (quoting, almost verbatim, his introduction to “Jazz’s” companion coffee-table book), “by the notion that if we continue to try hard, we’ll have a chance to hear Louis blow Gabriel out of the clouds.”

In “Jazz” the delight is in the details, and in the skill with which Burns puts them together. The bit of footage where Charlie Parker rolls his eyes at the camera in near-lascivious appreciation as he listens to Coleman Hawkins solo, and the one where sad-eyed Billie Holiday hangs on Lester Young’s every note, rapt with love. The now-grandfatherly Dave Brubeck bursting into tears remembering a black neighbor from his childhood who bore the scar of a brand on his chest. The young Armstrong, all teeth and tuxedo, singing and playing a manic, rhapsodic “Dinah” (“If I had to take one piece of film to the grave,” Burns says, “that would be it”). Burns’s own tour de force: an elegiac montage of still photos of city life that goes on for the entire three minutes of Hawkins’s famous 1939 “Body and Soul.” And an unforgettable moment when absolutely nothing happens: the usually voluble and articulate Wynton Marsalis begins a disquisition by saying, “Race is…,” and then ponders for 13 long, long seconds. “He stopped and paused,” Burns recalls, “knowing as a good media guy that I’m going to cut and begin again, right? But I knew, being a good media guy, that I was going to keep the whole damn thing.”

Burns and his team interviewed 50-odd musicians, from the late Doc Cheatham (who once played with Bessie Smith) to such new jacks as Joshua Redman, and critics including Gary Giddins, Stanley Crouch and Albert Murray, who all served on Burns’s 21-member advisory panel. Researchers assembled 3,000 pieces of music (the film uses 498), 1,000 hours of footage and more than 15,000 still photographs for those trademark Ken Burns shots in which he pans across a grainy old photo as if it were a landscape. The triage became increasingly painful. Critics like The New Yorker’s Whitney Balliett are already faulting Burns for giving too little attention to any number of important musicians: Charles Mingus, Bud Powell, Erroll Garner. But for Burns, the shape and coherence of the film took precedence; he cut 20 minutes on Powell down to a glimpse, because it was “too many notes.” (He doesn’t mean Powell’s piano-playing.) “I left out many more generals in ‘The Civil War’,” Burns says. “They just didn’t have asvocal advocates.” After watching him configure and reconfigure a couple of minutes of the Mark Twain film, you know the six years it took to make “Jazz” didn’t include much downtime.

And for Burns, when a film wraps, the promotion begins. “I’m going to Los Angeles, San Diego, San Francisco, Seattle…” and he names nine more cities, in order, without looking at his itinerary. “In each place, it’s like four or five interviews and an evening performance thing where I show clips and talk. They’ve already sold out a thousand tickets at some exorbitant price for me and Joshua Redman. The next night it’ll be 300 big PBS donors and Susan Stamberg interviewing me. Meanwhile you’re getting up to do morning TV, you’re signing books at noon at the… whatever.” But he must like it, right? “I love it,” he says. “Evangelism!”

Not everyone will be converted. Despite Burns’s insistence that he hasn’t bought into any particular view of jazz history, his film leans strongly to the neoclassicist analyses of Murray, Crouch and Marsalis–“the evil triumvirate,” Burns says, wryly acknowledging the hostility they evoke from less conservative critics and musicians. Jazz, in this view, is a dance-based music (though hardly anybody’s danced to jazz for 50 years), which by definition has to swing and thrives on the tension between improvisational freedom and rigorous musical discipline; both tennis-without-a-net “free jazz” and the jazz-rock fusion pioneered by Miles Davis are at best intriguing sidetracks and at worst aberrations or betrayals. Although the broader-minded critic Gary Giddins actually gets more screen time, Marsalis, always ready to demonstrate a musical point with his horn, seems to anchor the film. For Burns, it must have been irresistible to begin and end his story with master trumpeters from New Orleans–and anyway, at heart he agrees with Marsalis. Why would he not? A filmmaker so meticulous that he chooses an atmospheric city car horn because it’s in tune with Armstrong’s “Stardust” can sympathize only so much with jazz’s anarchist-liberationist wing. “Wynton is excoriated because he actually believes this, this and this is jazz, and this, this and this isn’t,” he says. “How unfair. But taste and discrimination are the hallmarks of civilization.”

Nevertheless, Marsalis’s circle-the-wagons esthetic and Burns’s decision to squeeze 40 percent of jazz’s history, from 1961 to the present, into 10 percent of his air time make you wonder whether this film, so full of life and music, isn’t in fact a memorial to a dead art form. As the narration notes, jazz now accounts for less than 3 percent of record sales–back in the Swing Era, it was about 70 percent–and today’s post-Wynton stars, the Roy Hargroves, Nicholas Paytons and Joshua Redmans, are essentially playing the music of the early 1960s. Hasn’t jazz simply run its course? Hasn’t it all been done to death?

“I know what you’re saying,” Burns answers. “It’s like painting has run its course. You have abstract expressionism and bebop, right? Audience drops away. Then you’ve got pop and op and conceptual, and finally you get to the point where people are saying art is whatever I think it is. Same thing happened in jazz. But then you had Wynton and others saying no, it’s a discipline. If you continue with my painting analogy, it was like the reintroduction of a representational style, the Lucian Freuds, the Kitajs. And I have a gut feeling–and maybe it’s completely foolish–that jazz is poised on the brink of something new. I think it can fuse with popular music again, as it did in the ’30s, and be hugely entertaining. Because if anything, Americans need to swing. I hope you’re wrong that jazz is dead. Because I firmly believe if there’s no jazz there’s no us. It’s like the canary in the mines–if that canary dies, get the hell out.”

Hmm. Jazz restored to economic vitality and cultural centrality? Even in an idyllic post-hippie New Hampshire town, where every third car seems to be a Saab, this sounds utopian; in the rest of America, 17i years of PBS documentaries wouldn’t usher in a new Swing Era. What Burns really seems be doing with his educated guesswork is what he acknowledges he’s been doing in his films for 20 years: trying to “wake the dead.” And even his profound concern with race in American society is ultimately personal. “I’ve spent years thinking I was doing Who Are We–hiding, for whatever fear of death, behind the ‘we’,” he says. “But really, it’s Who Am I?”

This is the story he tells. “My mother had cancer every moment of my life,” he says, “until she died when I was 11. At 3 years old, I was this little grownup. All I remember is her dying, and me sort of transferring the cancer that was killing my family to the cancer that was killing my country. Because all the civil-rights stuff was going on then, the hoses and the dogs in Selma. I’d stay up all night worrying, supposedly about race, but it was obviously about my mom. And that’s where the race and the history in my films come from. A few years ago, when I was going through a painful divorce, I told somebody that I thought I was keeping my mother alive, that I hadn’t really closed it at all. He looked at me and said, ‘What do you think you do for a living?’ I said, ‘Excuse me?’ He said, ‘You make Abraham Lincoln and Jackie Robinson come alive–who do you think you’re trying to wake?’”

So it’s that simple. Anxiety about mortality. Waking the dead. It even explains Burns’s most characteristic technique, those slow, close-up pans across damaged old photos: 3-year-old Billie Holiday, the pupils of her eyes leaping out as scary black dots; Buddy Bolden in 1905, an apparently handsome blur framing eyesockets and a lower lip. The longer and the closer we look, the more vividly the dead come back–yet the more we recognize that we’re only looking at their images. And the same goes for the living. “Our most important work and our most important relationships are the ones that get our full attention,” Burns says. “That’s the birth of wisdom–staying with it. And yet you also have to acknowledge that plasticity, that impermanence. You have to let Billie Holiday dissolve into grains.” In “Jazz,” Burns doesn’t really make history come alive. Who can? But for 17 1/2 hours, he does manage to fight time to a standstill.

So what’s the big mystery? Only this: the mystery of creative intuition itself, which somehow knows that you must choose 13 seconds of nothing, or a shameless shot of the full moon. It’s a mystery that Burns has the sense to let be, and that the musicians in his rocking, swinging, joyously blaring “Jazz” leave in blessed silence.