WASHINGTON (AP) _ When Marie Hartley whistles, people can't help listening.

It was her piercing blast - with right thumb and forefinger pinched in front of her teeth - that won Ms. Hartley a leading role in the National Symphony Orchestra's current performances of Sergei Prokofiev's ''Ivan the Terrible'' in the Kennedy Center Concert Hall.

It was at the first rehearsal of the music that Prokofiev originally wrote for Sergei Eisenstein's 1940s film classic that Ms. Hartley, an alto with the 180-voice Choral Arts Society of Washington, attracted the attention of conductor Mstislav Rostropovich.

The orchestra and singers had begun practicing the ''Song of Fyodor Basmanov and the Tsar's Men,'' the rowdy chorus of drunken soldiers in a tavern courtyard, when Rostropovich tapped his baton and announced that he need a whistler.

A few male singers whistled unimpressively. ''Then I thought, oh, they need a whistler?'' Ms. Hartley said. ''So I really let it go. He stopped and said, 'Who did that?' I raised my hand and he said, 'You, you're the whistler.'''

Later in the week, another five singers had been judged loud enough to make up a chorus of whistlers, but Ms. Hartley remained the virtuoso.

Her whistle is not for gently summoning the family dog. It's more appropriate for hailing a taxi three blocks away in rush-hour traffic, or overcoming the hellish racket at a rock concert.

The athletic Ms. Hartley, a 26-year-old massage therapist, special education teacher and champion Frisbee player from suburban Bethesda, Md., is at a loss to remember how or why she began whistling so expertly.

''I don't know,'' she said, ''I've always been able to do it.'' It just came to her, probably about the time she also taught herself to juggle softballs while waiting for the referees to show up for a high school game.

The other whistlers in the chorus, practicing informally before a recent backstage rehearsal with the orchestra, demonstrated that there's more than one way to split an eardrum.

While Ms. Hartley whistles by forming a circle with thumb and forefinger on one hand, freelance writer Kandy Stroud tucks an extended finger from each hand into her mouth, just as she learned from a childhood chum on a backyard swing.

Lawyer Toni LeBel uses a different technique to stop taxis on downtown streets. She shoves four fingers into her mouth, two from each hand. But psychologist Richard Plies doesn't use any fingers. He merely whistles with his lips and tongue, which is the way he answered his father's call to the dinner table as a boy.

Ms. Hartley's championship women's Frisbee team is called ''Satori,'' a Zen Buddhist term meaning enlightenment or - in her liberal translation - ''being at one with the Frisbee.''

''That's the way I whistle,'' she said. ''I'm at one with my whistling.''