White man at the door; one man's mission to record the "dirty blues" - before everyone dies.(R.L. Burnside)

R. L. Burnside sits in a folding chair backstage at the Village Underground, in New York, mopping his brow with a towel and sipping from a half pint of Jack Daniel's. With his hair upswept in two graying wings from his massive forehead, he resembles an impishly smiling version of the famous portrait of Frederick Douglass. At seventy-five, Burnside exudes a jaded, bullish vitality. Wearing red suspenders over a faded flannel shirt, hunter-green pants, and muddy yellow work boots, he looks as though he's just come from a day in the fields, driving a tractor -- which is the way he has supported himself for most of his life.

Well-wishers are surging backstage; one by one they approach and then crouch down to pay their respects. Introductions are conducted by a dishevelled young white man, rail-thin in a T-shirt and jeans. This is Matthew Johnson, the head of Fat Possum Records. At almost any hour of the day, Johnson gives the impression of having just got out of bed after a sleepless night. Without benefit of gel or deliberate grooming, his short sandy hair achieves that pointing-in-seventeen-directions-at-once look that's become so fashionable in recent years. Despite the triumphal nature of the occasion -- a sold-out, celebrity-ridden New York gig by a musician whom he has almost single-handedly rescued from poverty and obscurity -- Matthew Johnson has the worried, resigned expression of a man who knows that things can only get worse -- and will.

"R.L., this is Uma Thurman," Johnson says in a weary drawl.

"Matthew tells me y'all are in the movies," Burnside says politely, and promises to look out for her pictures when he gets home to Mississippi. Debra Winger says hello. As Richard Gere approaches, Matthew Johnson reminds Burnside that he has met the actor before, when he played at Gere's recent birthday party in Manhattan. "Oh, sure," Burnside says. "I remember him. He had all them monks at his party." The bluesman had never heard of Richard Gere; his concern was whether the gig paid in cash. He was worried about endangering his monthly welfare check.

"That was one of the good gigs," Johnson remarks. "R.L. actually showed up for that one."

For the past decade, Johnson, who is thirty-two, has made a mission of finding and recording the last of the Mississippi bluesmen -- the inheritors of the legacy of Charley Patton and Robert Johnson -- making him perhaps the last in a long line of white blues entrepreneurs and preservationists from Alan Lomax to Leonard Chess, although he speaks disdainfully of "blues geeks" and is a controversial figure in the blues community. (A recent Fat Possum compilation was called, provocatively, "Not the Same Old Blues Crap.") Crisscrossing Mississippi, the poorest, most racially divided state in the Union, Johnson knocks on the doors of trailers and shotgun shacks, chasing down rumors of guitar-playing tractor drivers and welders, searching for the living remains of a tradition that stretches back to the beginning of the twentieth century. ("I wish I had a dollar for every time I heard some kid shout, 'White man at the door,' " Johnson says.) His discoveries are not necessarily the best singers or guitar players in Mississippi. Johnson is looking for something else -- something raw and original, a kind of authenticity that some might call soul. "All I care about is that they have a signature," he says. "I can find a guitar wizard in every mall guitar shop in America."

Fat Possum now has a stable of septuagenarian bluesmen, and a following that includes Bono, Beck, and Iggy Pop (who describes Fat Possum as "the most uncorrupted label in America"). Mississippi blues -- as opposed to Chicago blues -- is supposed to be acoustic and folky, but the Fat Possum sound is grungy, repetitive, and amplified, more back alley than front porch. In many ways, it seems closer to punk rock than to, say, the jazzy virtuoso riffs of B. B. King, or the polite homages of Eric Clapton. Some have called it "dirty blues," although that phrase is almost laughably redundant.