Karl Goldmark's Violin Concerto is one of the more demanding pieces in the Romantic-era repertoire, and Hilary Hahn shimmered through it Saturday night at Broad Run High School in Ashburn. From the measured martial opening to the showy third movement, the Loudoun Symphony Orchestra, led by Mark Allen McCoy, kept up with her--but just barely--as she swept through the virtuoso passages and a difficult cadenza with aplomb.

Hahn insists she's not a prodigy. But with or without the label, she has had a remarkable career. The 19-year old violinist, who was born in Lexington, Va., and grew up in Baltimore, began studying violin seriously before she was 4. She played her first solo recital at 10 and performed with the Baltimore Symphony Orchestra throughout her teens.

David Zinman, the musical director emeritus at the Baltimore Symphony, became her mentor. Now, as a recent graduate of the Curtis Conservatory in Philadelphia, Hahn is a seasoned soloist with a recording contract and return engagements with major orchestras in the United States and Europe.

During an interview before a rehearsal, Hahn discussed her Loudoun Symphony performance as she looked forward to playing the Goldmark concerto in public for only the second time. The first was with the orchestra at the Interlacken Music Festival.

"It's lyrical in the style of the late 19th-century Romantic era," Hahn said. "During the early part of this century, it was played often by Nathan Milstein and other violinists but suddenly fell out of fashion." Hahn heard a recording of Milstein playing the Goldmark and decided to add it to her repertoire.

"I find the piece rewarding to play, and the orchestration is unusual," she said. "I like the ornamentation and harmonies and the way orchestra and soloist interact." Later this year, she plans to perform the Goldmark again in Vero Beach, Fla.

On Sept. 11, Hahn returns to the Washington area to play with the National Symphony Orchestra. Her fall recital tour takes her across the United States and to Europe, including a performance with the Berlin Philharmonic in December.

When she's touring, Hahn's father travels with her. "He helps with little things so I can practice and gives me company on the road. He gets food for me," she said with a laugh. Her mother, she said, is a finance executive in Baltimore and can't get away.

Wherever she goes, Hahn sends postcards to her Web site, part of www.sonyclassical.com. The idea grew out of a visit to a class of third-graders in Upstate New York--Skaneateles, on one of the Finger Lakes--during a music appreciation program.

"The kids were just starting a geography class, so I decided to send a postcard from everywhere I went that year," Hahn said. "Then their teacher retired, and I transferred the postcard program to my Web site."

The section, called Hilary's Journal, contains a couple of dozen postcards from the road. "I write a postcard or letter-length text on my laptop and send from each city I'm in, adding photos from a digital camera," she said.

On stage, Hahn is a talent to be reckoned with. Her technique is polished and athletic, clean and brisk. The fugato section of the concerto, a rumination in the style of J.S. Bach, unwound like a thick velvet ribbon.

At times, one wants her to stretch for richer emotional nuance, something that surely will come with time. The Goldmark concerto--and the Allegro from Bach's Sonata No. 2, which Hahn played as an encore--showcased technical command rather than deep passion.

During the extended intermission, families with eager music students thronged around the table where Hahn sat autographing recordings.

Her first, released in 1997 by Sony Classical, features Bach's solo partitas and sonatas and won the French award 1998 Diapason d'Or for young talent. The second disc is the Beethoven Violin Concerto and the Bernstein Serenade with the Baltimore Symphony Orchestra, David Zinman conducting. Next, she plans to record the Barber Violin Concerto with the St. Paul Chamber Orchestra, Hugh Wolff conducting.

"I like to record," Hahn said. "It's very intense. I like to play through larger sections to get a whole feeling of the piece, then go back and touch up smaller sections." The hardest part of recording, she said, is listening to all the playbacks and deciding which passage to select. "But it's very educational--the one time you get to listen to yourself."

Saturday's program resumed with the Loudoun Symphony presenting Dvorak's Symphony No. 8 in G, Op. 88. The symphony's pastoral serenity offered a contrast to Hahn's flashy playing.

The orchestra's wind section lacked a few voices, and on the crowded high school stage it would be difficult to squeeze them in, but the flutes and oboes distinguished themselves, especially in the plaintive Orientalist melodies in the second movement, as did the cellos in the fourth.

The far-from-ideal acoustical environment--tile walls, cement floors, loud air conditioner--gave the orchestra a shallow, tinny tone, which is a shame. The musicians of the Loudoun Symphony, and its guest artists, deserve better.

CAPTION: Hilary Hahn, who began studying violin seriously before she was 4, says she is no prodigy, despite a remarkable professional career.