Don-don -- don-don. Pat-too-pah, pat-too-pah -- Boom-Boom-Boom-Boom.

Bells, rattles and drums mount to cacaphonous heights, and the rhythm is contagious. Some of the apprentices, six to sixteen, are even chewing gum in time to the beat. But their teacher, Yacub Addy, son of a medicine man from Ghana, is not quite satisfied.

"Let's try it again," he says. "Listen very carefully to what I'm playing here: ba-ba -- ba-ba-ba." Addy is beating out the rhythm on a metal bell -- which, his wife, Amina Pournarus, explains to a visitor -- is the time-keeper in all West African rhythms.

"I'm seeing new faces," says Addy, as more kids stream into the basement of the Anacostia Branch Library. "Maybe they don't know the names of the bell and the shaker. My tribe -- the Ga tribe from the area around Accra, the capital of Ghana -- call the bell the ngonngon . But the Ashantis -- you know about the Ashantis -- call it the adaranta . Say it after me: ah-dah-ran-tah." The kids stumble a bit, but Addy smiles. "Well, you only have to remember one of those words." Plus, of course, a couple of names for the rattle -- the Ga word, dug , or ahase , which is what the Ewe tribe calls it. "The Ewe tribe is from Ghana," explains Addy. "But when you go to Togo or Dahomey you see the same tribe."

Jessica and Ahene, both ten, are issued bells and Afua, eight, gets a rattle, but Ahene isn't quite sure what they're supposed to do. "Mr. Yacub, she starts first, and then I start, and then she starts?" asks Ahene. Yacub nods and starts playing another rhythm on a drum called a giddi .

"Wow, I could never do that -- play one pattern while he's playing another," says Addy's wife, admiring the girls."I'd start playing what he's playing . . . In Africa, men would play the drums, and girls would play the bells and shakers and certain kinds of drums, but Yacub makes no distinction. His best pupil in Seattle was a white woman."

Yacub starts to dance to the music, and the boys, waiting their turn to play, are tapping their feet. "Americans don't realize that African music is really very complicated," says Pournarus. "There are so many different rhythms going on at one time." But Addy, showing eleven-year-old Charisse how to rattle the shaker -- twice against the thigh, then once against the hand -- seems to contradict her.

"That's all," he tells the student. "It's very easy . . . Now the men. Where were you last week?" "I had to go to a tennis lesson," explains a boy with a red-white-and-blue wrist band. In drumming as in tennis, Addy says, the hands must be firm but not stiff.

When Addy is satisfied that everybody has the basic drumbeat down pat, they put it all together. Three boys take the drums, two girls play the bells, another kid shakes the rattle and two little kids get extra drumsticks to bang together or on their chairs. Georgette, six, gets tired and starts chewing on the end of her drumstick instead, but Addy soon gives her a chance to play the bells. Timorously, she beats out the pattern, and the older kids applaud.

The two-hour session is almost over but, twelve-year-old Coretta reminds Addy, they haven't done any dancing.

"Okay, let's dance," Addy agrees, and a line forms behind him. "You push your leg and keep your foot flat. Don't do like that," he warns, tapping on his heel. One-two, one-two, he walks across the floor, bending forward from the waist. One-two, one-two, stamp the sneakers, sandals and flip-flops behind him. "This is called the Gahu ," explains Addy. "It's a social dance. You can do it anytime."

The drum and dance classes, according to the Reverend Kwabena Brown of the Southeast Cultural Institute for the Arts, which sponsors the program, have been going on for about five weeks. Later, says Brown, the kids are going to make their own costumes. "I'm coming every week," says Jessica, mentally replacing her soccer T-shirt with something more spendidly ceremonial. "Maybe we'll be in a show!"

Addy learned drumming and dancing during the rituals his father performed as a medicine man. Addy and his brothers became locally renowned and were often invited to perform at Ghanaian festivals. Alarmed that western music and dance would crowd out the traditional arts, he later founded a troupe that played on television in Ghana and traveled to Europe and America. "Now I am trying to dispel so many misconceptions that have been spread about my culture in this country," he says.