Up in the fourth-floor cafeteria at Roxbury’s O’Bryant School Wednesday afternoon, David France had split five young musicians into two groups.

In one corner, two clapped along to a beeping metronome.

In another, three played through a few measures of a tune, again and again, until they got the section just right: the right bow placement, the right notes, the right attitude – that extra oomph on the down-beat when the song bursts into its theme.

“That’s great,” France said when the trio nailed it, his own violin clutched in his left hand as he prepared to play along. “Let’s do it two more times.”

Five days a week for three hours a day, the Roxbury Youth Orchestra meets here, its 20 members – pre-teens to early 20-somethings - passing through three days a week in chunks of a half-dozen or so, practicing their skills on pricey instruments provided for next-to-nothing.

For the privilege, they pay $60 for two terms of instruction. It’s a bargain compared to what most youth musicians’ parents would pay for that much attention from a skilled instructor. But it doesn’t pay for it all – the trips, the snacks, the repairs - and it doesn’t pay France or his rotating team of volunteers more than a small stipend.

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And it can’t sustain the program forever. So for the first time since its inception three years ago, France is asking for crowdfunded cash on Indiegogo to keep the program going.

“Orchestra in the Hood,” he calls the campaign. They need $15,000, he said. They’re about half way there.

“We don’t really have much,” said Shirley Wong, a 20-year-old Simmons sophomore who’s been with the program since she was in high school. “We’re not asking for much either. We’re just asking for our teachers, our instruments and our peers.”

The Roxbury Youth Orchestra stands out. There isn’t another program like it in the city, France said. There isn’t enough demand, let alone room in the budget, to teach string instruments in most Boston schools. Many families, in a district where three out of four students qualify as low-income, can’t afford lessons.

“There are opportunities for elementary school, but then they dry up in middle school and high school,” France said. “Allowing someone to pick up a string instrument at 11, 12, 13, 16, 17, that’s almost nonexistent.”

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Apart from Boston Public Schools letting France use the cafeteria space, he relies solely on donors – some of whom throw him coins and dollar bills when he plays in MBTA stations, often five days a week.

Other benefactors he meets online, where he has a wide following. In the Twitterverse, he said proudly, he’s the top influencer of the hashtag #YouthOrchestra.

A follower once sent him a violin from the Netherlands. Another flew him to Chicago, where, in exchange for leading seminars and coaching another after-school program’s founder, he got to take a bundle of equipment back to Boston.

But many of the donated instruments need repairs France can’t afford. And his six volunteer instructors, only three of whom are paid anything at all, deserve to be compensated for their time and energy, he said.

His students don’t just learn, they perform - sometimes for big audiences. They’ve toured as far as Portland, Maine and played at local colleges and the Museum of Fine Arts. France said in 30 concerts over three years, more than 10,000 people have heard them play.

Some of their songs, about a third, are originals.

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It “builds confidence,” France said, to walk into an after-school club one day, then play the classics, hip-hop and funky, one-of-a-kind tunes at Harvard or North Station in a few short months.

It also forms bonds, the way only a band can, he said.

“We play together as a family,” said Nardos Gosaye, 16. “That’s the main thing that I’m here for, really, besides playing the violin.”

It doesn’t matter whether any of his students become professional musicians, France said. Music makes youth “intrinsically motivated,” he said, and that lasts in any environment.

“If you can play the violin, one of the hardest instruments in the world,” he said, “you’re gonna believe that you can do anything.”

RYO’s fundraiser on Indiegogo has two weeks remaining. It’s also accepting spare instruments. And students.