I first met Vassar Clements in the early '70s when he came to one of promoter Jim Clark's "Peace, Love, Blues and Bluegrass" festivals. I don't remember if it was at Watermelon Park in Berryville, Va., or at Aunt Minnie's Farm in Stumptown, W.Va., but I do remember that actually seeing Vassar finesse those astonishing melodies and improvisations from his fiddle added richness and resonance to an amazing sound that had only recently been recognized outside the bluegrass world.

With his sculpted features, Vassar looked like the meticulously carved head (absent the beard) gracing the peghead of his instrument -- a 400-year-old violin given to him as a Christmas present by singer-songwriter John Hartford. After Clements's death Tuesday in Nashville at 77, one can imagine a signature Vassar Clements fiddle topped by a facsimile of the hard-bowing virtuoso.

It hardly mattered who brought Vassar to the festival all those years ago -- most likely, it was Earl Scruggs -- because he seemed to sit in with everybody, not only with the many bluegrass, folk and rock acts on the weekend bill but also at the impromptu picking sessions taking place all over the festival grounds and often going well into the night, lit by the glow of campfires and gas lamps. Whether with grizzled veterans or inspired amateurs, Vassar made no distinctions, and you could just imagine him saying, "Anybody want to pick a little bit? I'll back you up."

Which is what Vassar did for much of his career, starting in the late '40s as a member of Bill Monroe's pioneering ensemble the Blue Grass Boys. After years of faceless session work in Nashville, Vassar's fortunes began to change in 1971 when Hartford's "Aereo-Plain" album briefly brought together the Dobrolic Plectral Society, featuring Vassar, guitarist Norman Blake and dobro player Tut Taylor, foreshadowing the contemporary song-driven genre known as Americana.

That same year, Vassar got the call that changed his life. It was from John McEuen, whose Nitty Gritty Dirt Band was about to embark on a special project bonding country, bluegrass and rock musicians -- what became the bestselling classic "Will the Circle Be Unbroken" album. The idea had been to provide exposure to a wider audience for the likes of Mother Maybelle Carter, Roy Acuff, Scruggs, Merle Travis and Jimmy Martin, all pioneering country and bluegrass artists who had been rejected by the modernized Nashville establishment.

As McEuen recalled yesterday in a telephone interview, "When I asked Earl Scruggs if he'd found a fiddler . . . he said, 'Yes, his name is Vassar.' As I then didn't recognize his name, I asked if he could cover it all. Earl's quiet confidence in his 'He'll do . . . ' was, well . . . never was that statement such an understatement. After a couple of days' rehearsal at Earl's house, I thought: 'How are we going to hold up to this guy?' "

Clements's name was added to the front of the album as one of the stars, "because he was," McEuen said.

Clements's signature song on the album, "Lonesome Fiddle Blues," inspired the instrumental section of the Charlie Daniels hit about a hot country fiddler, "The Devil Went Down to Georgia." For the next decade or so, no fiddler was hotter than Vassar Clements.

More important, the album brought attention to a singular style melding the rhythmic riffs and bluesy swing of jazz and the virtuoso improvisation of bluegrass, a hybrid Clements eventually dubbed "hillbilly jazz," defined by an approach so smooth and dynamic that it earned him the nickname "Superbow."

In the 1970s, Vassar signed on with the hugely popular Earl Scruggs Revue as bluegrass enjoyed one of its cyclical commercial comebacks, and in 1973 he teamed up with Jerry Garcia, David Grisman, Peter Rowan and John Kahn to form Old and In the Way. That bluegrass group was Garcia's nod to the traditional music that inspired him in his pre-Grateful Dead days.

Old and In the Way was short-lived: Over a year, the band played fewer than 50 shows. But one of them took place in June 1973 at a bluegrass festival at Lake Whippoorwill in Warrenton. The circumstances are hazy, but I ended up picking up the band members at BWI airport, driving them to Warrenton, then hanging at their hotel as they jammed into the early morning hours with fellow musicians before a midday appearance. The glue that held those jams together was Vassar's fiddling, at least partly because he always seemed more interested in being complementary than in being dominant. No doubt he was a virtuoso, but he was never an egotist.

That reflected Vassar's personality. He was quiet, soft-spoken and, says McEuen, "the worst swear word he ever said was 'dad bime,' as in 'Dad bime, that fiddle won't tune!' It was his own word -- I never heard it anywhere else. I don't think I ever heard him say a bad word about anyone, and he was more interested in you than you might have thought, learning about the people he was with."

Over the decades, he was with many people, in thousands of recording sessions, hundreds of concerts. Clements could sit in with anybody, equally comfortable playing bluegrass, jazz, country and rock -- preferably all at once.

Twenty years ago, he shared a truly memorable bill at the Birchmere with the Texas R&B guitarist and fiddler Clarence "Gatemouth" Brown. Both had an aversion to stylistic boundaries, so the night became an astounding and invigorating conversation about American music that embraced the bluegrass of Flatt and Scruggs's "Foggy Mountain Breakdown," the western swing of Bob Wills's "New San Antonio Rose," the galloping jazz of Duke Ellington's "Take the A Train" and more, with Clements and Brown effortlessly weaving in and out of each other's vivid inventions. And at night's end, the biggest smiles belonged to the musicians.

Vassar Clements's style, dubbed "hillbilly jazz," was so smooth and dynamic it earned him the nickname "Superbow."