"Play a little something," the photographer asked. So Anne-Sophie Mutter, a 16-year-old in blue jeans and sneakers, chewing gum removed, picked up the fiddle and tuned it. Screech, screech -- tuneless violin squawks of no particular character.

Suddenly she paused, and then ripped into a chunk of a Mozart concerto, and the hotel room filled with music. Rich, full, sparkling music. She stopped, took the instrument from under her chin, and smiled. "Thank you," the photographer said.

At 16, Anne-Sophie Mutter is sometimes described as a "former child prodigy," which seems somewhat semantically picky. Tonight, as one of the National Symphony's youngest guest soloists in recent years, she will play a Mozart concerto conducted by Mstislav Rostropovich.

"I hear in my life many wunder-kind," said Rostropovich, who himself first performed in public at age 13. "Mostly these people have a great talent for technical things. What impressed me about Anne-Sophie is that she has a real, deep feeling for music."

The maestro first heard her two years ago in Paris when they both appeared in a television birthday salute to her mentor, Herbert Von Karajan. "I immediately invited her to play with the National Symphony in Washington," he said. "And she said, 'If you speak with my parents!'"

Her parents, William and Gerlind Mutter, came with her from West Germany to Washington, and with their help and translations, allowed their daughter to be interviewed recently -- something they do not often permit.

The life of a child genius can be notoriously difficult. Pushed by overzealous stage parents or held captive by unscrupulous managers who exploit the novelty of youthful virtuosity, the legendary image of a child prodigy is not an enviable one. They supposedly grow into neurotic adults, perhaps artistically successful, perhaps not.

Anne-Sophie Mutter seems to have escaped this fate. She had never been forced to practice, it seems; rather, it is she who wants to spend time on her music.

Where other child prodigies are often thought to be technically proficient but without the soul that comes with maturity, she "made music from the first day," her father said.

"From the beginning she had only cheap little violins," he said. "But they always had a sound that reached you."

When her parents speak of their daughter's accomplishments, they do not seem to be boasting. Instead there is a feeling of surpise in their words, as though they are amazed to have produced a child with "such a precious gift."

In a brief encounter, she seems cheerful and sunny, respectful of her parents, a fairly normal teen-ager who likes the Rolling Stones in addition to Beethoven, likes to eat steak and French fries after a concert, and keeps pictures of musicians she admires inside the case that holds the Stradivarius lent to her by the West German government.

After she won her first music prize (at age 6) a manager wanted to promote her career as a child prodigy. "We did not want that," her mother said. "We wanted to let her grow up like other children and have the chance to develop."

And that's exactly what they seem to have done. Anne-Sophie laughs when asked whether she ever gets stage fright; the idea seems never to have entered her mind.She laughs when asked whether she ever gets bored practicing; "nein," she says firmly. She giggles when her mother is asked whether her daughter keeps her room clean; "three times a year," Gerlind Mutter says, "and I'm grateful for that."

They live in a small West German town (pop. 12,000) called Wehr, near the Swiss border. William Mutter works in the management of a newspaper, the Sudkurier. Neither he nor his wife is the least bit musical.

"Her elder brother heard Menuhin play and he said, 'I would like to play the violin.' And she was asked, 'and what would you like?' She was a little girl and she said very seriously, 'violin.'"

Anne-Sophie was then 5 years old. Nine months later she and her brother won a youth music competition in Erlangen. She won with "auszeichnung," her mother said: special distinction.

"The jury said, all these years we have secretly waited for the extraordinary. Listening to her, we even forgot we were a jury."

When she was 10 years old, a "catastrophe" struck: her beloved violin teacher, the only one in Wehr, died at the age of 79. For sixt months Anne-Sophie practiced alone. "To look at her and know she has no teacher . . ." her mother shook her head sadly at the memory. Eventually another was found, an hour and half drive away in Switzerland.

She met Von Karajan after playing with her brother at the Lucerne Festival in 1976. "Von Karajan was told by other musicians, 'You must hear this young musician,' and he invited her to come to Berlin and play for him." She played Bach's chaconne, "one of the hardest." She winces at the memory.

Anne-Sophie made her debut with the Berlin Philharmonic in 1978. The first night, even the musicians applauded.

"She was often asked, how long do you have to study every day?" Mrs. Mutter recalled. "She was -- um -- nasty. She said, 'I don't have to study.'"

In fact, Anne-Sophie practices three or four hours day, about six days a week. She doesn't play on Sundays and holidays "but even then I think about it," she said.

She has private tutoring to prepare her for college entrance exams, the "abitur." She likes to swim, and walk her dogs, do yoga, and "cook and eat."

Her latest record with Von Karajan, recorded when she was 14, was a best seller this Christmas in Germany. One side of the record, Mozart's concerto No. 3, was recorded in one take, which was supposed to be a rehearsal. She has appeared at the major music festivals in Europe, with major conductors. As the notes on the record album say, "The gateway to an international career is open to her."

"I am only a mother and I only hope for her to be happy," said Mrs. Mutter. "I am looking at her as a young girl, a young woman to be happy in whatever she's doing. We have not thought of careers."