In an age when teenagers might seem interested only in rap or rock music, there's a classical music oasis in Northern Virginia that keeps expanding its territory among youths, drawing young musicians not only from across the Potomac River but from as far away as Lynchburg. And after more than three decades, the Northern Virginia Youth Symphony Association is developing a sterling reputation among adults, too.

The association, with its top-level American Youth Philharmonic orchestra, will celebrate its 35th anniversary with a benefit concert Sunday night at the Kennedy Center. Music Director Luis Haza has recruited National Symphony Orchestra director Leonard Slatkin for his annual guest conducting slot, and Haza will play violin on Beethoven's Triple Concerto along with National Symphony colleague David Hardy on cello and Sara Wolfensohn on piano. The program, which also will feature works by J.S. Bach and Benjamin Britten, will benefit not only the philharmonic but the association's three other classical youth ensembles.

That's right: four hearty groups that continue to attract fierce competition for the limited number of slots in each. The string ensemble has 55 musicians, mostly very young children; the junior orchestra has 71 players; the Virginia Youth Symphony has 99 musicians, and the philharmonic has 102 players. Haza, who conducts the philharmonic when he isn't playing first violin for the National Symphony, said more than 600 teenagers now audition each year for the various groups.

"It's very competitive," Haza said during a break in rehearsal last week at Langley High School. "This provides a very important background, not only in music but in helping them gain acceptance to medical school or law school, and it makes them more well-rounded."

The Fairfax Symphony created the first two youth orchestras in January 1965, and 65 musicians in two groups made their debut that May under the baton of Gerald Brobst, a retired high school orchestra director. A third orchestra was added several years later, and in 1978 the Northern Virginia Youth Symphony Association was created as a separate entity.

Haza, 49, who joined as music director and conductor in 1984, added the string ensemble and began taking the philharmonic to international competitions and tours, including a trip to Russia in 1998. He also arranged collaborations with professional groups and renowned musicians, such as trumpeter Arturo Sandoval and clarinetist Paquito D'Rivera. "When we get to play with such great artists," Haza said, "it's a great testimony to the quality of the program we have."

Unlike many youth orchestras, the American Youth Philharmonic plays a full season of five or six programs, rehearsing weekly with Haza at Langley. "I want to expose them to the major works--challenging, but not too difficult," Haza said.

The reviews indicate he has succeeded magnificently. In 1996, longtime classical music critic Joseph McLellan wrote in The Washington Post that the philharmonic "probably ranks higher among student orchestras than the NSO among the world's major orchestras. Its 100-plus players perform consistently at the level of a good, professional adult orchestra, and many American cities would be lucky to have it as their resident symphony."

Almost 3,000 musicians have played with one or more of the four ensembles in the symphony's 35-year history, and many have continued to distinguish themselves in the arts. Most notable among the philharmonic's alumni is Alexander Kerr, an Alexandria native who is now concertmaster of the prestigious Royal Concertgebouw Orchestra of Amsterdam. Other noted former Northern Virginians include Lynne Ramsay, assistant principal violinist of the Cleveland Symphony Orchestra; Jeremy Kurtz, called "the most important young double bassist of the next decade" by Strad magazine; Valerie Vigoda, the singer and violinist for the rock band groovelily; and Dermot Mulroney, an actor who starred in "My Best Friend's Wedding" with Julia Roberts and is a former cellist with the philharmonic.

"Every state I go to with the NSO," Haza said, "I meet my alumni, whether they're musicians or doctors or lawyers, even in Alaska. And in Montana, I met a young lady with her own youth orchestra, and she had been our principal clarinetist 15 years ago. We have a tremendous legacy."

The philharmonic's reputation isn't limited to students in Northern Virginia, either. It has stretched at least to E.C. Glass High School in Lynchburg, where 16-year-old Stephen Meyer decided he had to travel to Northern Virginia to audition and where he eventually became co-concertmaster and one of the orchestra's principle violinists.

"The players are so much better, and the education is so much better," Meyer said. He makes the three-hour drive with one of his parents every Monday, hoping this is one more step on the path to becoming a professional violinist.

Laura Woollen, a 17-year-old senior at Robinson High School in Fairfax, acknowledged that the early years of viola lessons didn't make it easy to stay interested in classical music. But, she said: "It's a whole new world playing with an orchestra. You're like playing with a team, and you're all working toward an end product. It's like a sport, and it's much more enjoyable."

Haza also received high marks from his young musicians for his upbeat attitude and willingness to help individuals. "He's easy to talk to, a very nice guy," Woollen said. Elizabeth Adams, the co-concertmistress and a 17-year-old senior at Alexandria's T.C. Williams High School, said Haza is "very professional, but he's fun. I've learned a lot from being in the orchestra," which started for her in fifth grade.

Tracy Roussey, the symphony association's executive director, said the orchestras have been able to continue attracting top-notch talent in part because of the large number of professional musicians in the area who then teach youngsters and in part because "these are just ageless instruments, and the music is timeless." Roussey said her young musicians still go home and listen to pop music, but she hears occasionally of converts.

"One parent told me she was excited when her son got in the car one night and changed the radio to the classical music station," Roussey said. "And another parent told me she was listening to the classical station and her son said, 'I've played that.' "

CAPTION: Northern Virginia Youth Symphony Association Music Director Luis Haza, top, conducts the philharmonic group during rehearsal at Langley High School in McLean for a 35th anniversary performance. Above, violinist Grace Song, a Langley junior, plays.

CAPTION: Sofia Rotter embraces fellow oboist Keri Humphreys during rehearsal.

CAPTION: Music Director Luis Haza pauses on the violin to confer with guest cellist David Hardy.