NEW YORK — Roberta Guaspari's voice is ragged from overuse. She's spent the last two months rehearsing students for a violin concert at Carnegie Hall and has to strain to make herself heard over their playing and chatter.
"It's not like I'm shouting in an angry way, but it's 60 little kids, a lot of them from elementary school," she explains in a husky whisper.
The notion of listening to dozens of children saw away at stringed instruments would be enough to inspire shudders in most. But for Guaspari, the founder of Opus 118 Harlem Center for Strings, it has become her life's work.
This year's benefit concert, called Fiddlefest and held Tuesday at Carnegie Hall, was the latest demonstration of her efforts. It opened with Guaspari's students playing a richly harmonized — and screech-free — version of "Jingle Bells." Midway through, vocalist Bobby McFerrin walked on stage to improvise percolating vocal lines over the students' playing.
McFerrin was the first in a string of famous musical guests. Yo-Yo Ma, Itzhak Perlman, Joshua Bell and Regina Carter also performed, and the decidedly unmusical newscaster Tom Brokaw (who described his singing voice as "a weapon of mass destruction") introduced Opus 118's corporate and artistic honorees.
But the focus was on Guaspari and her students, who also performed selections by J.S. Bach, Karl Jenkins and Dave Grusin. On the Grusin piece, the students played a flowing Latin melody over congas, bass and two percussionists.
The concert marked the 10-year anniversary of the first Fiddlefest at Carnegie Hall, which raised $250,000 for Opus 118 in 1993. The intervening years have seen the 54-year-old Guaspari stage similar benefits at Lincoln Center, the Apollo Theater and Central Park.
Along the way, she has become something of a celebrity. The 1999 movie "Music of the Heart," starring Meryl Streep, was a dramatization of Guaspari's life, and the first Fiddlefest was the subject of the Oscar-nominated documentary "Small Wonders" (1995).
Her story began in 1991, when she was working as a violin instructor at three public schools in Harlem. Laid off because of budget cuts, she started giving private lessons at her house on 118th Street in East Harlem (hence Opus 118's name).
As her program became better known, donations increased, allowing Guaspari to hire assistant instructors and to open a community music school last year. In all, 400 students are served in a program with an annual budget of $600,000.
Guaspari has also returned to two of the public schools where she used to work, and her assistants teach at four others, offering lessons to first- and second-graders. The schools, all in Harlem, subsidize the instructors' salaries and pay for students' instruments.
The public school lessons remain the backbone of Opus 118, Guaspari says, and there's never a lack of students interested in taking lessons.
"I started music lessons in public school and that's why I'm so committed myself to kids who would never have the opportunity or means to take lessons like we're providing," she says. "My real mission in life would be to bring that back, to allow all children to have access to a good quality music education."
Asked about her teaching style, Guaspari says she's tough but caring.
"To my students, the other kids say, 'Ooh, you're in violin, that's not easy,' " she says with a laugh. "I send notes home, I make a lot of demands. I'm not tolerant of anyone fooling around in my class."
But her students say they appreciate the tough love.
"It's for a good reason that she yells at us — to give us discipline and focus when we play," says 16-year-old Jose Rojas as he tunes his violin during intermission backstage at Carnegie Hall. He has studied the instrument for 10 years and says he'll continue in college.
"Discipline" and "focus" are words that arise often in conversation with Guaspari and her students.
"That's what studying music can teach them — the discipline, learning how to study," she says. "It can't help but transfer over to anything else they do in life."
She rattles off examples of former students who, even if they have not pursued music as a career, have gone on to top colleges and become doctors, lawyers and academics.
One Opus 118 alumna, Nora Friedman Weiss, now 24, went to Wesleyan University in Middletown, Conn., and now teaches violin at a public school in New York.
"What makes Roberta so effective is that no matter how old the kids are, when they enter the room, she treats them very seriously. They have a very important job to do there," Weiss says.
Another goal, Guaspari says, is boosting self-esteem.
She remembers one former student who was ostracized because she was taller than most other girls her age when she began lessons. But her playing progressed rapidly, and Guaspari let the sixth-grader perform a solo at a school concert.
The performance was a turning point, Guaspari says. The girl's fellow students were mesmerized by her playing, and she's now at Walnut Hill performing arts school in Massachusetts.
"The violin brought such beauty into her life," Guaspari says, her voice hoarse as she sighs. "It's amazing what music does."
On the Net: www.opus118.org