COOKIE SPAETH says it's "kind of like grow-your-own," when he talks about the students at the D.C. Music Center. This nonprofit community music school takes beginners--the young and old from the inner city--and gives them a chance to learn and perform.

The center, which has about 125 students, was founded in 1970 by Honey Gorodetzky, widow of the late second violinist of the Budapest String Quartet. It is housed in All Souls Unitarian Church, itself a bustling center of community activities and home to the Mount Pleasant Montessori School and Columbia Heights Youth Club. Two years ago, a satellite center was established at the Episcopal Church of the Atonement in Northeast Washington.

Working professionals teach both instruments and voice in private lessons to the students. Those professionals also make up a jazz ensemble that is playing tonight at 8 in a benefit concert for the school. The concert, to take place at All Souls, also will feature jazz pianist and vocalist Shirley Horn and WRC-TV news anchor Jim Vance as emcee.

Native Washingtonian Horn studied music at Howard University and has played the local club circuit here for more than two decades. Among her early fans in the 1960s was Miles Davis, who was so impressed with her first album that he invited her to perform at New York's Village Vanguard. Last month, eight albums later (and a ninth, recorded at the Corcoran, in the can), Horn returned to the Vanguard. Her recent travels have included appearances at the North Sea Jazz Festival in the Hague and an engagement at Ronnie Scott's in London. Locally she is at the One Step Down every Sunday, is scheduled for a set at the Kool Festival in the Kennedy Center on Sunday, June 5, and in August will share the bill with singer Joe Williams at a Fort Dupont concert.

"The jazz ensemble is now set as far as having this many members, and these are the people who always have been and always will be in it," said Spaeth, who joined the music center's faculty in 1974 and has been its director since 1979. Musicians for this concert will be Simba Douglas, trumpet; George Oakley, saxophones and clarinet; Bob Diener, piano; David Jernigan, bass; Louis Cotton, guitar; and Ivan Sargent, drums. All but Diener are on the faculty and all are active as performing musicians.

Jazz is only one kind of music taught at the center: Isabella Bates, for example, teaches classical voice and Oakley teaches reed instruments in both jazz and classical. Percussion instructor Broderick Shappell performs with area rock groups and is a member of Caiso, a Trinidad steel drum band.

Events sponsored by the center will include an annual fund-raiser called a "Musicathon"; student recitals at the Church of Atonement on June 5 and at All Souls on June 11; an appreciation dinner and fund-raiser on June 9; and a five-day music summer day camp.

"We also go out into the community and do free concerts," Spaeth said. "We've been to Forest Haven, Lorton Reformatory, D.C. Jail, senior citizens centers and children's centers. It's to both give students exposure and to take music into these institutions."