After changing the lives of more than 500 New Haven children through music, a husband and wife are turning their attention to two other kids ­­— their own.

Nine years ago, Tina Hadari MUS ’04 and three other string musicians founded Music Haven, a non-profit after-school organization that teaches string instruments to children from low-income New Haven neighborhoods. Since its founding, the scale of the organization has grown significantly: The same quartet that used to meet in living rooms now has its own office, a communications director and a larger budget, and the number of students enrolled has nearly doubled in just the past five years. This fall, Hadari announced that she and her husband, Netta Hadari MUS ’99 — who serves as the development director — will pass the reins to someone else in order to focus attention on their family.

“I’m really committed to seeing Music Haven thrive and grow, but at the same time I’d be making a mistake if I didn’t model the kind of life and family that I wish for all the children and families in Music Haven,” Tina Hadari said.

The executive director position will be posted in early November, and a board-led search committee will begin interviewing potential candidates in January 2015. Once hired, the new director will work alongside Hadari until she steps down on June 30.

Although several members of the organization attributed the non-profit’s success to Hadari, they also said the organization is currently positioned to continue its growth under new leadership. Colin Benn, the quartet’s violist, said he is excited about entering the next phase of Music Haven under new leadership because the group could “go in any number of directions.”

The core of Music Haven’s programs is currently the free music lessons and string instruments provided to 81 children from New Haven’s Empowerment Zone — a collection of congressionally designated underserved neighborhoods. Each member of the Haven String Quartet — Music Haven’s resident quartet — gives music lessons on weekday afternoons and performs in New Haven on some weekends. Each student enrolled at Music Haven, aged five through 16, receives two private lessons each week, except for first-year students who have group lessons. All costs are covered under Music Haven’s budget, half of which comes from individual donations. The rest of the organization’s funding comes from foundations, the government, the earned revenue from quartet performances and corporations.

In the coming years, the organization hopes to expand into untapped neighborhoods to reach a broader range of New Haven students, said Yaira Matyakubova, one of the quartet’s violinists.

“Our secret mission is to infiltrate the city with music,” said Netta Hadari, adding that currently, application to the program is highly competitive, with over 20 children currently on the waitlist.

To reach the point that Music Haven is at now, Tina Hadari said it went through a few challenging years. She said starting the organization in New Haven was especially difficult because the town houses a lot of transients. Due to the high number of groups that originate in New Haven and then move elsewhere, neighborhood residents do not expect permanence from local start-ups. She mentioned a four or five year time frame after which the community trusts an organization and is willing to partner with it.

Gregory Tompkins, one of two violinists in the quartet, attributed the growth of Music Haven to Hadari’s leadership. The diversity of the board members she recruited also contributed to the continued success of the program, he said.

Parents from the organization also praised Hadari for her commitment to the program.

“[Tina and Netta] didn’t have a life until her first baby was born. They give everything to the kids at Music Haven,” said Becky Jones, whose granddaughter Denasha also takes music lessons through Music Haven.

Inez Valezquez, the mother of a student at Music Haven, said the program and the string quartet had given her son, Noel, excellent role models. Noel shows up to rehearsals even when he doesn’t have to, she said.

While the Hadaris are unsure of their plans for next year, they both feel optimistic about what the future might hold. Tina Hadari speculated that both she and her husband would continue to work for social justice in some capacity.

“The world is open to us right now,” Netta Hadari said.

The Haven String Quartet’s first concert of the 2014–’15 season is this Saturday at the Unitarian Society of Hartford and is titled “The Architecture of Sound.”