It is the mark of modern virtuosi that they can transcend the limitations of musical genres and instill vivid color and character in a range of material.

Three string masters, playing in Washington Sunday, reflect that variety: guitarist Chet Atkins and mandolin player Jethro Burns (at the Smithsonian's Baird Auditorium) and hammer dulcimer player John McCutcheon (at the Barns of Wolf Trap).

What connects all three is an eclectic repertoire drawn from the vast reaches of Americana.

Because Atkins has so often surrounded himself with pop gloss (after all, he took country music uptown when he invented the Nashville Sound), it's sometimes easy to forget what a marvelous and influential guitarist he has been in the last 30 years. Atkins once confessed a disdain for most of his studio albums, which have pitted the expansive, chance-taking player against the conservative, perfectionist producer. "The Best of Chet on the Road . . . Live" (RCA AHL1-3515) suggests that Atkins' recent move to CBS, after a productive career at RCA, might be necessary to free him from his own pedestrian formulas; there are fine moments on the RCA collection, but they wrestle with the mundane.

Among the better cuts are a fluid retelling of John Hall's "Dance With Me"; Sousa's "Stars and Stripes Forever," in a neo-classical setting that provokes some finger-fireworks; a swinging "When You Wish Upon a Star," with a lovely harmonic subtext; and the sparkling, Spanish romanticism of Atkins' own "Recuerdos de la Alhambra." Atkins has blinding speed and hand coordination, not unexpected in someone who manages impossible-to-finger melody lines played against chords without ever succumbing to blurred notes, squeaks or buzzes. Atkins' technique -- influenced by the gypsy swing of Django Reinhardt, the rolling cadence of Merle Travis, the interpretive gentility of Segovia and the restless invention of Les Paul and Eddie Lang -- is always anchored by a relaxed feeling that could easily lull a listener into thinking it's all too easy.

On a half-dozen cuts, that feeling-unswinging sophistication is inescapable: a Beatles medley is clever but predictably slick; a "Freight Train-Chattanooga Train" medley with French guitarist Marcel Dadi quickly runs out of steam after a lovely, pavane-like beginning; "Blind Willie" sounds like bad Jim Croce; and "This String" is a bland introduction to the guitar strings. And Atkins sings the way most people play guitar -- with sincerity. One feels this is just another record (Atkins' 80th or so) with bright moments but no lasting shine. On to CBS.

Atkins' pal Jethro Burns is another country music tradition, not only for his 39 years as half of the country-comic team of Homer and Jethro but because he's been one of the most distinctive mandolin players of his time. "Tea for One" (Kaleidoscope F-14) is solo Burns, with a few stories and funny introductions that confirm he still knows how to get a laugh -- the softly swinging Mitchell Parrish-Peter De Rose classic, "Deep Purple," is "dedicated to my wife's varicose veins." But for all the grinnin', it's the pickin' that stands out, from a Neapolitan-flavored "Sophisticated Lady" to an intricate and self-echoing reading of Antonio Carlos Jobim's "Wave" to the dexterous, bluegrass virtuosity of "one of my originals, I call it 'Rip Off.' "

Burns invests this collection of pop chestnuts (including "All the Things You Are," "Willow Weep for Me," "Crazy Rhythm," "Tea for Two" and "No Greater Love") with distinctive twists -- bluesy breaks, choppy chords, piercing tremolos -- that never interfere with melodic integrity; he may embellish like a madman, but he never abandons a tune. There's some Reinhardt gypsiness at work here, as well as the insistent edge of the great Russian mandolinist, Dave Appalon. At one point Burns says, "Mandolins as a rule don't have much fun because people are always pickin' on 'em." Producer David (Dawg) Grisman has wisely kept things so uncluttered that one hopes Burns' classic red mandolin gets picked on a lot longer; it won't get picked on much better.

John McCutcheon may be the least known of the string virtuosi here, but his new album, "Fine Times at Our House" (Greenhays GR710), is very much the best, with less familiar but splendid material and a warm esthetic that imbues the entire album with a special grace. Actually, McCutcheon spends almost as much time here on fiddle as the hammer dulcimer, but he's often double-tracked so that he complements, rather than competes with, himself. He's also aided by a circle of friends, including the members of the outstanding West Virginia string quartet, Trapezoid.

There are five vocal selections, ranging from the intense celebration of Si Kahn's "Wild Rose of the Mountain" (which segues into some splendid, glassy twin fiddling) to the high, lonesome mountain air, "Times Are Not What They Used to Be" (haunting harmonies curl around terse fiddle lines).

"Samanthra," a truly moving shape note (sacred harp) hymn, has a sparse dulcimer and cello bottom that sustains the song's Renaissance aura even though this form of congregational part-singing still survives in America's mountain churches.

Just as impressive are the seven instrumentals, including the primitive player-piano exuberance of "Hale's Rag" and "Backside of Albana/Colley's Reel," the utterly infectious "Nancy Ann/Hey John D. Where'd You Get Your Britches," and the harpsichord-like lamentation of the Irish harp tune, "Carolan's Farewell to Music." Best of all, though, are two waltzes, the lullaby lilt of "Granpa's Waltz" (which segues into a delightful polka) and "Amelia," an achingly romantic tune by Bob McQuillen that starts off with the fiddle dominant before ending with an added dulcimer track. Like some of Trapezoid's work, it has a folk-chamber music feel to it, a woodsy baroque quality enhanced by the nostalgic innocence of the hammer dulcimer. "Fine Times at Our House" is a wonderful celebration of acoustic grace.