BILL MONROE is the champagne of the bluegrass world -- opening a club or kicking off a new festival without him would be unthinkable. Several weeks ago, he helped reopen the Birchmere, moving on the next morning to the First Annual Preakness Bluegrass Festival in Baltimore; he appears at Wolf Trap this afternoon and tonight. "It's been a bunch of them," the taciturn Monroe says of his appearances at such openings. "I'm proud of all that. I'm glad to go ahead with it and carry it on just like I brought it down through the years. I keep the music going near right as I can."

In the dressing room of the Birchmere, the stately Monroe sits against the wall, quietly picking out an aimless warm-up on a 25-year-old mandolin that's all but lost its lacquer. Monroe, a man of few words, sits in a somber suit, a flowing mane of white hair trailing from the back of his ten-gallon white hat. As other band members come in and pick up their acoustic instruments, they slide into Monroe's melody; it's a tradition that dates back to 1939, when Monroe started the original Blue Grass Boys in; Kentucky. Since then, he has been not only the originator but also the driving force behind the continually expanding popularity of a genre of music that took its name from his band.

What makes Monroe's evolution from pioneer to patriarch so unique is that, at age 71, he's playing his music pretty much the way he did in 1939 when he first went on the Grand Ole Opry. Then, the music's surging beat and new style of harmony singing -- what came to be known as "the high lonesome sound" -- blew in like a breath of fresh air. Four decades later, there's very little age on songs like "Muleskinner Blues," "Footprints in the Snow," "Kentucky Waltz" or "Blue Moon of Kentucky" (which became a hit for the young Elvis Presley as well). Next month, MCA will add a new album of Monroe instrumentals to the 50 or so he has out already, yet Monroe sounds like a man beginning a career, not capping it. "I went on the Opry in 1939, and it went to growing, you know. It's taken a long time."

"I love bluegrass music and I have willpower, there's nobody I know could change me," Monroe insists quietly. "I was going to play it the wasy I thought it should be played, the way I knew my friends and fans would want me to play it."

The roots of Bill Monroe's music live in Rosine, Ky., between Louisville and Paduca. Two older brothers, Charlie and Birch, took up guitar and fiddle; mandolin was all that was left for a shy but stubborn proud farm boy who grew up surrounded by string band music and blues. Bill Monroe first tested his voice in the open fields; his ears, meanwhile, took in a wide variety of secular and religious folk traditions and styles, from the radio and live, and the young Monroe spent many hours playing at local dances. The three brothers left home and worked the oil refineries around Chicago before catching on as a regional square dance band. Between 1936 and 1938, Charlie and Bill did very well as a traditional country and gospel brothers-style duo, successfully recording for Bluebird, but failing apart personally after frequent ego conflicts. In 1938 they separated, Charlie forming the Kentucky Partners and having his own, smaller career.

Bill Monroe's bank started off as the Kentuckians before adopting the name the Blue Grass Boys in honor of their home state. Their success on the Opry made Monroe into a major star, to the point in the late '40s that he traveled around the country performing in a huge circus tent -- and with his own baseball team. "There was a time when baseball in small towns kind of died away, you know," Monroe says wistfully. "And I had to work hard on my music. Bluegrass went to growing more, so I had to give all that up." He still has a full stable of foxhounds and drives friends crazy by insisting on showing farmers tricks learned on the Kentucky ground.

In 1945, the Boys were a veritable hall of fame: Monroe on mandolin and high tenor, Lester Flatt on guitar and harmony tenor, Chubby Wise on fiddle and a young banjo player named Earl Scruggs. Other famous alumni include Jimmy Martin, Sonny Osbourne, Mac Wiseman and Don Reno; the current band features the fabled fiddler Kenny Baker. Though the music reflected a staggering array of influences -- from Jimmie Rogers to a local black businessman, Arthur Schultz -- "I wouldn't take much of their music for mine," Monroe says. "I was going to make sure bluegrass didn't copy nobody. Now, you'll find some Scots bagpipe . . . Methodist, Baptist and holiness singing . . . some blues and a little jazz and swing to it, but you don't ever let that override the whole thing."

The spare, strident harmonies of ultra-traditional shape-note singing reappeared in bluegrass vocals. Monroe's phenomenal mandolin approach was, on the other hand, totally new -- its close-chorded syncopation was powerful and explosive, a joyful extension of the square dance beat. What Monroe did, and what he continues to do today, was to meld the fire of tradition with a certain modernity that stops short of electricty. Bluegrass echoed tradition, and over the years the words Monroe, bluegrass and tradition have become interchangeable.

By the late '40s, Monroe had spawned not only influence, but imitators. He left Decca Records when they signed the Stanley Brothers, whom Monroe felt sounded too much like him. In the '60s, when Flat and Scruggs were getting much of the credit for originating the music because of their visibility via "Bonnie and Clyde" and "The Beverly Hillbillies" theme, Monroe went into a deeper shell than before. Introspective and shy because of extremely poor eyesight, Monroe had always let his music speak for him, and the country people he came from always accepted that. But the urban-centered folk, revival of the '60s asked questions and sought out connections. Monroe's laconic attitude did little to advance his reputation, and for many years the father of bluegrass felt like he'd been disowned.

"I might have had that feeling," Monroe says now, "but about that time, people would come along and let me know I was the one who done it, put it together, and that I would never have to worry. That cleared all that away."

Monroe's incredibly high tenor is slightly frayed 51 years after his first radio broadcast in Indiana; he returned home there to Bean Blossom more than a decade ago and bought the Brown County Jamboree, turning it into his own ongoing refuge for traditional bluegrass festivals. Monroe was seriously ill and in the hospital several months ago, but, he says, "I came out of it all right. I think I'm getting back together, though the doctor told me not to overdo anything."

That last instruction may be the most difficult for Monroe, who has taken his music around the world many times, from festivals in cow fields to Carnegie Hall in New York, and Albert Hall in London to the White House. Monroe has watched in amazement as Japanese, German and Swedish bluegrass bands performed phonetically perfect reditions of his classic tunes without speaking another word of English. "It's a wonderful music," he explains. "It's got a lot of good meaning in it, it's music that brings people together and makes friends. It's also close to gospel -- and the people that love the music can feel that in there. The feeling in the music is bound to touch their heart."

That feeling extends to bluegrass musicians, too. At the Birchmere, the Seldom Scene engaged in one of bluegrass' oldest traditions, picking classics with the originator himself. Monroe laughs, pointing out that "this is one kind of music that you don't have to get together and run over "hings to play. In bluegrass, they can hear it and when it comes time for a break, they know what to do. They all can play together."