YFs aren't quite like Valley Girls. YFs take phrases like "too much retard" and "too heavy and broad" musically rather than personally. They aren't like yuppies or preppies either; they don't worry about IRAs or alligators. They have other things on their minds -- like auditions, chamber music repertoire, and whether to attend a music conservatory or a general university.

YF, coined by the education department of the National Symphony Orchestra, is shorthand for "Youth Fellowship" students -- an ensemble of 19 young musicians, herded and aided by Carole Wysocki, the education director. The Youth Fellows are area high school students who study music on scholarship with the National Symphony -- usually for a three-year period.

One of the program's highlights is Wednesday night's "Meet the Orchestra Concert": Eight Youth Fellows will put on their black duds and join the NSO in two movements of Dvorak's "New World" Symphony. Tickets for the concert, which begins at 7 p.m. in the Kennedy Center's Concert Hall, are a modest $3.

Begun in 1980 with a grant from the D.C. Commission on the Arts and Humanities, "the program was originally conceived in hopes of helping move talented people who might not otherwise realize the full extent of their talent," says Linda Harwell, an NSO bassoonist and a Youth Fellowship teacher who has taught three Youth Fellow bassoonists.

From private, once-a-week lessons to open rehearsals, from master classes to seminars, the students, in effect, observe their future lives as musicians.

"I had a pretty good guess beforehand," says Rachel Young, referring to the realities of the music world. Young, a junior at Woodrow Wilson High School, is in her second year with the Youth Fellowship program. She studies the cello with David Hardy and Wednesday night will perform with the orchestra. The fellowship program, she says, "has made it all the more real. It's not a guess anymore."

Beyond the realistic picture it provides for the would-be professional musicians, the program offers students a competitive edge. Hardy observes that Young, by dint of her education through the fellowship program, has "quite a jump on other people . . . It is an elite situation that spurs each of them on, to think even further about music."

Both the fellowship students and their teachers emphasize the educational value of having a teacher who is a musician -- a teacher who not only performs several times a week with a major orchestra, but also takes on solo and chamber engagements. "Most of my students come and hear me play outside of the orchestra," says Hardy. Last Thursday evening, for example, Young watched Hardy perform in the Terrace Theater, in trio with Eugene Fodor and Arlene Portnoy.

"I always make sure my students understand what it means to be in music, how difficult it is -- not in the pessimistic sense, but that it is difficult and you have to be good to be successful," says Hardy.

Nineteen-year-old Michael Lee, a bassoonist studying at the Philadelphia College of Performing Arts, was a student at the Duke Ellington School of the Arts, and for two years an NSO Youth Fellow. Lee compares the experience to attending a college preparatory school, and says that "there wasn't anything they wouldn't do for me, music-wise. If I had a problem making a tape for a college audition or preparing for a certain recital, they were always there to help."

The rapport between the aspiring musician and the working musician makes the program particularly unique. Harwell, Lee's Youth Fellow teacher, observes that the program "institutionalizes the role of the teacher as a mentor" and allows the students "to become part of an extended symphony family."

In a sense, the Youth Fellowship program validates the experience of "hanging around." Whether lingering backstage or in the Kennedy Center's canteen, the Fellows shadow their teachers and busily absorb the rhythms and mechanics of daily orchestral life. Backstage, Young has "made a lot of friends. Instead of being a kid surrounded by grown-ups and feeling stupid, I feel welcome -- like one of the musicians . They tell me what to look for in a piece, which conductors are good, which aren't, what to listen to."

Exposing the students to thought-provoking situations and then answering the questions that arise is a vital part of the educational philosophy at the NSO. At open rehearsals, which last for 2 1/2 hours, the Youth Fellows watch from Concert Hall box seats, wave to their NSO pals (like the lighthearted timpanist Fred Begun), and follow attentively the "orchestral parts" on sheet music.

Often the group reconvenes in a rehearsal room for a question-and-answer session with representatives from the orchestra, board members, management and the staff. Several weeks ago, Rudolph Vrbsky (oboist), Toshiko Kohno (flutist) and Marcia Gittinger (assistant NSO librarian and free-lance violinist) gave brief autobiographical sketches and then fielded the students' questions, imparting bits of practical advice and generic wisdom gleaned from their experiences.

One girl, with her sights set on Eastman School of Music in Rochester, N.Y., wanted Kohno's advice: Should she choose a music school for one particular teacher or for the school's overall quality? Kohno, who attended Eastman, said she had really chosen the teacher rather than the school. "The school turned out fine, too." The crowd chuckled.

"Was it a letdown to graduate from a music conservatory and end up teaching in a high school?" one blunt student, acutely aware of the odds, asked Gittinger (a teacher at Hayfield, a Virginia high school).

"Was it frustrating -- I mean, competing with hundreds of other flutists?" another inquired of Kohno. The answer: "There's always room at the top."