Parents are used to hearing that school budgets are putting the squeeze on activities like music and sports. But rarely has a solution to such a problem been as elaborate and artistic as the “Symphony for a Broken Orchestra.”

The Pulitzer- and Grammy-winning composer David Lang was commissioned by Temple Contemporary, the art gallery at Temple University, to create the symphony to help solve a problem: The Philadelphia school system has more than 1,000 broken instruments and little money to fix them.

Around 400 musicians, a third of them students in the public schools, will perform the piece on Dec. 3 at the 23rd Street Armory in Philadelphia on some of those broken instruments.

Now based in New York, Mr. Lang grew up in Los Angeles.

“I thought, ‘I am a musician because there were instruments in my school,’” he said. “I had a visceral response to this project. Every one of these broken instruments is a kid who won’t have a life-changing experience. I am getting upset right now just thinking about it.”

After the show, for which tickets are free, the instruments will be repaired, using money from donations inspired by the performance, online gifts to “adopt” instruments and financial support from the Pew Center for Arts & Heritage and the Barra Foundation.

Repair kits will also be given to the schools, and a “legacy fund” endowment established. About $100,000 has been raised of the $1 million goal.

The initiative is an example of focused local philanthropy, something that strongly motivates donors, said Buff Kavelman, a New York–based philanthropy consultant.