Sometimes it must be galling when you're a brilliant young violinist and you're coming out of your teens and people still keep treating you like a child prodigy.

It came up last month at the opening of a midday chamber music concert at the Spoleto festival in Charleston, S.C. Young Joshua Bell of Bloomington, Ind., who will make his Kennedy Center debut with the Mostly Mozart Festival tonight, was about to appear on stage.

The master of ceremonies, the Lincoln Center Chamber Music Society's Charles Wadsworth, was describing all the remarkable milestones of Bell's career -- a recent European tour and Carnegie Hall debut with the St. Louis Symphony, a debut with the Philadelphia Orchestra at age 14, a recent appearance with the Cleveland Orchestra.

Then Wadsworth added: "There is one other thing, too. Josh just made a request. He came up to me and said, 'You know, it says in the program that I am 16. And I wonder if you couldn't tell the people that I just turned 17.' " The capacity audience roared.

Then Bell appeared, to play two dazzlers by Ysaye and Ravel, followed by a glowing Schumann Piano Quartet with three colleagues. He looked self-assured but not in the least smug. Clean-cut in a Midwestern way, he moved with the natural grace of the racquetball ace that he is.

It appeared that making music is all business to him.

"Some people have criticized me for not smiling more," he recalled over lunch during a subsequent visit to Washington. "But I always try not to look like a fool. And there's nothing worse than a fake smile, especially after a serious piece. Or even before it. The mood begins before the music and affects the music."

Bell is certainly beyond the stage of being a nervous kid -- he zooms around Bloomington in a prized Datsun ZX sports car that he said will do 130 mph. But since his mother had just arrived from a tour of Washington museums, he ducked a question on whether he drives it that fast.

He also claims no fear of the stage. "I look forward to going on stage," he said. "I enjoy pressure."

Leonard Slatkin, the St. Louis Symphony conductor who has been watching Bell's development for some time, noted there were three soloists on the recent tour -- Isaac Stern, pianist Emanuel Ax and Bell. "The European agents said that since Isaac and Manny were so established, it might be nice to bring along someone who was new and young, and I thought of Josh immediately."

Slatkin said that for all Bell's sobriety on the platform, "there is a spontaneity in his playing that one almost never hears from musicians his age. The most flattering thing I can say about him is that every time he played the Bruch or the Lalo on the trip, he never did them the same way twice. There was never anything that was really out of the ballpark. And he was very careful about following the tempo and the general shape of the music. And his technique is so fine that you take it for granted.

"But I kept hearing him make these little points of style that young violinists don't normally try in this age of note-perfect but cool recordings. There were portamentos and these little slides."

Slatkin attributed this stylistic freedom to two things: One is Bell's teacher, Indiana University professor Josef Gingold, one of the world's celebrated violin teachers. "Joe has this way of developing a player without trying to push him into a mold," said Slatkin.

The other reason, according to Slatkin, is that Bell has been able to develop in a more relaxed atmosphere than the pressure cooker of New York's Juilliard. "Josh is out in the heartland of the country, and you can hear that in his pure and natural playing."

Slatkin's only cautionary note: "He is growing very fast. And I hope he doesn't push himself too far too soon. I deliberately did not program the most interpretively demanding concertos with him on the tour. And I tried not to use him in the cities where he would get glaring exposure, like Vienna. But even then, agents were coming in from all directions. One good sign, I think, is that this summer Josh is going to Rudolf Serkin's chamber music center at Marlboro, Vermont, instead of filling the dozens of dates he could get."

Gingold said Bell was insistent about going to Marlboro. "I think if he just gets to play one Beethoven sonata with Serkin, he'll come away with a feeling of musical growth.

"Certainly he is self-assured," said Gingold. "But he is also modest. He doesn't have the notion that he is God's gift to music, though a lot of us do."

Later, in a restaurant, his violin resting in a case by his side, Bell dove into a steak sandwich and fries and started talking about instruments.

"This is a Guarneri del Gesu in the opinion of many the greatest of violins and it is borrowed for the European tour. I have to get it back next week. But then I'll be loaned another Guarneri del Gesu . The one I've got now used to be played by Stern and the one I'll be getting used to be played by Menuhin."

He recalled the giddy experience one day of going through the Library of Congress' matchless collection of instruments and playing several of them, including the extraordinary Joachim/Kreisler Guarneri, the instrument for which the Brahms Violin Concerto was written. "Of course, it's exactly the right sound for Brahms."

Gingold said Bell will not be able to have his own master violin until "he is worth about $200,000. But meanwhile it is good for him to be exploring all these others."

Bell said matter-of-factly that his talent comes from "dexterity. It is something you are born with. And the wonderful thing about music is that you have it there all your life."