A SERIES OF deep chords explodes from the guitar. Mantuila Nyombo looks straight ahead, at nothing. The music is jazz, and he starts scat-singing. Gradually the song slips into something Caribbean, then something fast and cool with fifths and diminished sevenths. And suddenly it is pure flamenco.

Nyombo can make a guitar say anything he wants. A teacher, he plays in public Thursday, Friday and Saturday nights, at the moment in El Azteca, which is part of La Fonda restaurant at 17th and R streets.

When you see him, and especially when you hear him, you understand that Nyombo is someone special. In 1965, at 16, he left Zaire, where he had been playing with a band under the great Kabasele, the Duke Ellington of Zaire. First stop was Paris, the Aero Club, later the Olympia. He learned French and English, to add to his five African languages. Got homesick, returned to Zaire to play with the National Orchestra.

"I got a lot of encouragement along the way," he said. "People like Gerard Madiata the opera singer and Gerard Kazembe, who can sing anything he hears even in a language he doesn't know. So I went back to Paris and got my B.A. from the Conservatoire Internationale."

Where, by the way, he won two first prizes for classical guitar. By 1970 Nyombo was playing with Hugh Masakela in New York, having toured Europe with various groups and as a solo concert guitarist. He earned his master's degree in composition at Catholic University here, and later was an instructor at Howard. Now he gives private lessons when he's not on the lecture circuit or teaching in the Bennington College summer program.

"I want to get back to Paris and make another record," he said. "I wrote a sonata for the guitar, and I'd like to get that down."

He also favors his "Song to a Special Friend," written when he was breaking up with his American wife Charlene. She lives in Chicago now, with their two small daughters. The girls visit him sometimes, and might even show up for the first number in his gig, dancing around the podium in their best dresses.

It's the versatility that you notice first, the repertoire that runs from Bach to Villa-Lobos and back to Flamenco. He loves the crisp beat of Zaire's traditional music, quite like Brazilian folk music but often centered on a hypnotically repeated single note.

After a while you forget the versatility and give yourself up to the subtleties of sound that Nyombo draws from his guitar--or the lokele, an African xylophone, or the 24-string kora. "I've always been playing," he said. "I started working on the guitar seriously at 9 in a Catholic school at Kinchasa."

Before that, it was just fun.

"My father was a teacher and architect, and he didn't like me getting into music. He didn't think it was serious enough. I'd make a guitar with one string out of a coconut, and he'd destroy it. He'd break it in the morning, and when he came home that night I'd have another one. I got my younger brothers doing it too. There were 11 of us."

A nightmare of coconut guitars to some, maybe, but for Mantuila Nyombo it was a beginning.