The English virtuoso violinist Kennedy may have shed his first name (Nigel) and perhaps his persistent nickname (the Nige), but he hasn't shed his unorthodox concert garb. At the Kennedy Center Concert Hall last night to perform with the National Symphony Orchestra, he appeared wearing wrinkled parachute pants hiked up to reveal mismatched socks and shoes of a sickly greenish hue. From the midriff up was equally bizarre: a shabby, sleeveless jacket covering a floppy pirate's shirt tied with a sash. The hair was as usual: strange tufts rising over an almost-shaved skull, as if borrowed from some sorry overcoiffed dog whose breed hails from remote mountainous regions of central Asia.

His stage presence was as usual, too--a mix of elfin adolescent abandon and strange martial arts poses, his legs sometimes spread wide, sometimes snapped together as if he meant to crush walnuts between his thighs.

At this point in a review of Kennedy, it's customary to say that none of this matters. It's the music that matters. But perhaps the two--eccentric behavior and musical brilliance--are finally, completely inextricable.

Nigel Kennedy, now into his forties, was one of the most brilliant English violinists of his generation. In the 1980s, the great heyday of irresponsible marketing by the major record labels, he emerged as a kind of bad-boy punk figure, except no one really believed it. His pedigree--he was a boarding-school boy who studied with Yehudi Menuhin--was just too good. And the strange accent--was it Cockney? from the Midlands?--seemed like a put-on.

He made good newspaper copy, and a few unfortunate brushes with rock-star misbehavior only helped. But it always rang a bit false and ultimately Kennedy's star began to sink to the horizon of celebrity. So he took some time off--the intermission before the second act--and emerged two years ago as . . . himself. Same garb, same accent, same musical ferocity.

In a world in which politicians can reinvent themselves overnight and shed the sins of youth like brushing so much dandruff off their shoulders, Kennedy's consistency is about as close to authenticity or honesty as a freakish celebrity can come.

To play like he does--with unmitigated feral intensity--is in itself freakish. Last night, he chewed up the Brahms violin concerto and spat it out in great bleeding chunks, dispensing with the usual niceties and relying on sheer emotionalism to carry the piece. Not many artists dare try this because it is, in the main, a self-defeating route. It becomes all about speed, volume and bold experiments. You strive not to be interesting or individual, but to be more raw and ferocious and desperate than anyone else the audience may have heard. It's daring and it almost always fails.

Kennedy brought it off, in part because one looks at him and says, he's not like other violinists, and that opens the door to hearing him that way. He has tapped into the elusive mix of theatricality and believable showmanship that made the great 19th-century virtuosos unforgettable to their audiences.

Not that there aren't problems. He produces naked and ugly sounds. He takes over a performance, jump-starting entrances and insisting on bizarre rhythmic oddities. And it's revealing that since he reemerged as the new and improved and not much different "Kennedy" he's been traveling, for the most part, with only two concertos, the Brahms and the Elgar. "Kennedy" the show is highly scripted, even the parts that aren't.

He was certainly the untraditional element on a program that was, perhaps, the most traditional concert program so far this season. Each of the three works was of its own world and time, discrete and complete unto itself.

Music Director Leonard Slatkin opened with a composer he knows well--Haydn--and a symphony that is irrepressibly charming--the Symphony No. 67. It was a genteel and witty reading, well articulated by the strings with accurate and balanced support from the small woodwind complement. It is a symphony woven of little surprises, unexpected divisions among different instruments of a familiar theme, occasionally quirky orchestrations, and lovely ensemble passages integrated--archaically--into the larger whole. The NSO's performance was a stroll down some foreign city street, replete with small and unexpected details that add up to a pleasant sense of disorientation.

Barber's cantata of American nostalgia, "Knoxville Summer of 1915," completed the program. Americans have a bad habit of feeling sorry for something indescribable and irrevocably lost about the past. This little tone poem for soprano and orchestra describes that forgotten thing, the nameless noun that comes after "I miss . . . " It is quiet and sensuous and haunting, and anything but consoling. The soprano was Linda Hohenfeld.

CAPTION: Kennedy, a combination of eccentric behavior and musical brilliance.