At 13, Sarah Charness is everything most teenagers want to be; pretty, well-spoken, accomplished, and ever so slightly sassy when mom asks a question. Her favorite piece of music, if she has to choose one, is Swan Lake. "You like the C.P.E. [Bach] and the Beethoven, don't you, Sarah?" her mother asks. "Yeah, but I like Swan Lake better," Sarah replies. Then, as she absent-mindedly pulls her feet into fifth position, left heel to right toe, she makes nice. "I like the C.P.E. and the Beethoven too, Mom."

Of course, most 13-year-old girls wouldn't know Tchaikovsky from Thai iced tea-and neither do most kids Sarah's age take their violin lessons at the New England Conservatory. But the Charnesses are no ordinary family; Sarah and 8-year old sister Jenny (violins), 11-year-old brother Dan (cello), and their parents, Deborah (flute) and Michael (piano), make up the Charness Family Quintet, an accomplished classical-music group that will be performing this Sunday at the Cambridge Center for Adult Education.

As Deborah points out, the kids care barely remember not playing an instrument. And they are, indeed, the happy results of a union born in music. Seventeen years ago, Michael Charness knew that he wanted to marry a musician. His boss's wife wanted him to meet a certain flutist who lived in New York City. "A friend was after me for two years to meet this guy," Deborah says. "But I wasn't going to fly to San Francisco for a man." Eventually, Michael flew to New York City to meet Deborah. "We went to Central Park," she remembers. "We took a run. We went to my apartment, a studio on the Upper East Side...and we played sonatas. Then we took a walk, and he said, 'I think we oughta get married,'" The friend who introduced them is, by the way, named Sarah.

Seventeen years and three kids later, music continues to fill a white colonial in Newton at all hours. Each child practices until bedtime, and Michael is sometimes at the piano until the wee hours. The living room holds a baby grand and a grove of music stands. Black-and-white pictures of the family-in concert garb, with instruments in hand-hang next to floor-to-ceiling glass-fronted cabinets where sheet music is shelved and alphabetized.

The kids, by their own admission, were never forced to play music. But music animates this household, and resisting clearly would have been like not learning to speak. Jenny chose the violin to be like Sarah-who seems to have chosen it out of a taste for, yes, bows. A favorite family yarn tells how Sarah, at age 4, stuck her first bow straight into her mouth. Sitting around a table set with apple juice and brownies, the children tell such stories the way other kids recall their first bike ride.

Music has even infiltrated Michael's day job. A neurologist by trade, he is now the director of the Performing Arts Clinic at Brigham and Women's Hospital, where he has noted that professional musicians, perhaps fearing for their careers, tend to discount the pain caused by grueling practice schedules. Yet the resulting problems can benefit from treatment. Deborah says that, after developing pain in his own hand, Michael learned from observing his own surgery: "He watched his own hand surgeon operate on his elbow, his ulnar nerve."

The three kids are sure that music will always be a part of their lives, but only Dan expresses any desire to follow in his father's medical footsteps. "I might be a doctor, just to gross these two out," he says, pointing at his sisters. Otherwise, the Charnesses are taking their place in a long line of musical families, from the Bachs to the Mozarts to the Oistrakhs to the Charnesses' neighbors in Newton, the Baverstams-where mom plays with some of her children.

For now, the hardest part, according to Sarah, is finding enough time for friends outside of music and ballet class, where she has made pointe. But Sarah won't give up her music and her dancing. She has incorporated the music into her sense of self. "It's how you know you're different from everybody else. It's how you know you're special, you're not just the average person."