Picture this: Ten black men are enrobed in orange dashikis or in Zulu ceremonial dress -- colorful headdress and loincloths, grass leggings, ankle bells -- doing exuberant precision choreography halfway between a high-kicking tribal dance and a smooth-spinning Motown routine. Now listen: Joseph Shabalala's sometimes guttural, always mesmerizing vocals float through and around tight, rhythmically compelling, undulating chorales -- sonorously deep because seven of those 10 voices are basses.

There is nothing besides those voices and that movement.

Nothing more is needed.

Ladysmith Black Mambazo has been extremely popular in its native South Africa since the late '60s, but America first discovered the a cappella group on Paul Simon's "Graceland" album, where they collaborated on "Homeless" and "Diamonds on the Soles of Her Shoes." During Simon's sold-out "Graceland" tour this summer, their exquisite singing and exuberant performance made them show-stealers. Simon, who produced their recent "Shaka Zulu" album, didn't seem to mind a bit -- and in fact, seemed most energized when he was singing with the group. Now they're here on their own, performing tonight at the Warner Theatre as part of a 30-city American tour.

The Simon connection began in Johannesburg in 1985. "It was surprising when I heard that Paul Simon wanted to talk with the leader of Black Mambazo," says the charismatic Shabalala, 46, a short, stocky man with an engaging nature and a warm smile. "I was not familiar with him." Shabalala did know some of Simon's songs, through a neighbor's greatest-hits package, but he was "amazed to learn that he was a friend of Black Mambazo. He didn't tell me how or when he heard Black Mambazo, but he said he wanted to record. Was it possible?"

When "Graceland" came out in 1986, there was considerable controversy about Simon's recording in South Africa in violation of a U.N.-sponsored cultural boycott of that country. Simon was also accused of exploiting South African musicians.

The uproar surprised Shabalala.

"When we grew up at home, we {musicians} used to work together, lend support to each other, compete with each other," he says. "When Paul Simon gave us this chance to see the world, all our people were glad at home. If there is somebody who maybe don't trust Paul Simon, I trust him ... The first day when he talked to me, he was talking like a trustful man."

He was also singing like a South African. "Paul Simon's harmony is family, Black Mambazo harmony," Shabalala says. "When he sang he sang like our people who grew on farm, because they sang what they feel." The only difference was technical: "Paul Simon takes the key from the organ. With us, the leader must know the key. When I start, the others know where to begin."

Black Mambazo's extraordinary harmony, Shabalala says, came to him in a long-ago dream, what he calls a "mental vision."

He grew up as one of eight siblings in a mud-grass hut in the district of Ladysmith, Emnabithio, about 200 miles from Durban. Like his brothers, Joseph Shabalala eventually sought work in Durban in the late '50s, weaving cotton by day, singing with a popular local group, the Highlanders, at night. Their regional vocal style was a product of the many male a cappella choirs that sprang up in the South African hostels housing the millions of black workers who had left their homes and families to work in South Africa's mines and factories.

The choirs held competitions, known as ngomabusuki -- "songs of the night" -- only at night, far away from the whites who tended to disparage black culture and customs; the songs sustained familial and tribal traditions and celebrated happier times. Shabalala started his first group, the Durban Choir, in 1958; in the '60s, they became the Black Ones, named after a kind of oxen. Immensely popular in the Durban region, they were eventually banned from amateur competitions because they always won. In those days, the voices numbered as many as 16, with as many as 10 basses.

But something was missing for Shabalala. "I feel all the time when we sing that there is something short," he says.

In the '60s he'd alternate between working in Durban and working on the farm, singing for family and friends and in the competitions. In 1964 he dreamed of a new kind of harmony -- and five years later Black Mambazo was born.

Shabalala has described his dream as a concert in which singing children floated between the stage and the sky; he says he simply copied their movements and harmony -- "a very nice harmony, a very nice melody, just voices in order, very nice voices" -- and made up his own words because he couldn't understand their strange language.

But Ezimnyama, the group he formed to realize his dream, wouldn't follow his lead. "I tell {the singers} that for this new thing, the new harmony, I want everybody to know how it is," Shabalala remembers, but even after four years, "they failed to catch the harmony. They are popular in parts of Durban and at home, but me, I feel that there's something wrong. I told them that there's something short and they said, 'No, you're mad now.' I said 'Okay, carry on,' and I left them.

"Then I start a new group in 1969. I teach them how to sing all the parts. And that group caught this harmony."

Drawn from Shabalala's own family and those of his relatives, they became Ladysmith Black Mambazo -- the Black Ax of Ladysmith. There were 10 empathetic voices: one alto, one tenor, seven basses and the leader's clarion baritone. No one could read music, so Shabalala taught (and still teaches) each part separately; he then improvised (and still improvises) over that incredible harmony.

The group's impact was immediate, both because of what it sang and because of how it sang and danced it. Black Mambazo reinvigorated Zulu traditions that had been in danger of disappearing.

"There is a big difference between the people who grow up in town and the people who grew up on the farm," Shabalala explains. "Those who grew up in town used to say to those who grew up on the farm when they arrived in town, 'You are stupid because you don't know the street, you don't know how to dance as we do.' Same as when those who grew up in town went on the farm: 'They don't know the Zulu dance, they don't know how to expand the oxen, they don't know how to hold the shields.'

"I grew on the farm, where there is no gramophone, there is no radio, there is nothing there. We sing together with gals and then one man will stand there and do the Zulu dance -- pick up your foot and hit the floor hard ..."

Ladysmith Black Mambazo invented a variation on this dance style, in which the singers raise their feet in exaggerated high steps, but don't stomp. "When we arrived in town, people don't know our harmony, our dignity. When we sing they say to us, 'What type of music is this?' and we say isicathamiya {loosely translated as 'walking softly and proudly on one's toes so as not to be heard'}. We copy this music from the Zulu dance, but we are not hitting the floor now -- that's why we say 'walk proud.'

"And we are lucky, Black Mambazo, we take this music to the market. We are the first group who did that."

In the early '70s, the group sang live over Radio Zulu, and in 1972 they finally went -- reluctantly -- into the recording studio.

"We had arguments about people taking our voice," Shabalala recalls. "After that, what are we going to sing with? So we were walking very slow {to the studio}. We are too late and we said, 'Oh, we lucky. Our ancients were looking after us because they failed to take our voice.' "

When they finally started recording, Shabalala laughs, they still "tended to run away from microphones. {The engineers} had to work very hard."

Their first album was "Amabutho," meaning "Warriors," "because our songs follow the old customs ... We'd talk about the warriors and the kings because our fathers had told us about them on the farm."

There have been 25 more albums, all of which have reached gold and platinum levels (which in South Africa are only 25,000 and 75,000 respectively). In 1972 Shabalala finally quit his job as a mechanic to sing full time, but while he now owns several houses and drives a Mercedes-Benz, many of the other group members are still relatively poor. And for all the group's success across racial and political boundaries (there have been a number of European tours), Ladysmith Black Mambazo has never received any official recognition or support from the South African government.

In 1975, the group's focus began to shift following another Shabalala dream. "I heard a voice talking to me saying, 'You must fast for four days. By doing that you're going to defeat your enemy,' " he says. "I just did that; it was the first time not eating. I don't know nothing about praying."

Soon after, Shabalala's wife and two children were mysteriously ill and neither the town doctor nor the local witch doctor could cure them. A stranger appeared off the street, Shabalala says, and healed them with prayer -- "the disease running away."

He had been afraid to join the church, he says, because he was popular with women. But "January 1, 1976, that is the day I raise up my hands and said I dedicate myself to Jesus." He has since become a minister in the Pentecostal Church of God of Prophecy, and Black Mambazo's repertoire has become more spiritual -- though Shabalala points out that "the harmony is the same harmony which I caught from the dream, in every song. I didn't want to lose my harmony."

In the '70s, the group started singing in both Zulu and English, and the members have since learned to sing in several other languages, including German. "Many people like our harmony and we would like all of them to be happy and hear what we say," Shabalala says.

Some people, in fact, would like to hear Shabalala speak out against apartheid and the South African regime; a number of reporters and critics have tried to badger him into political corners. But he always slips out, serene and direct.

Even a song like "Homeless" -- which Paul Simon turned into a politically telling video -- has deeper meanings than apartheid, Shabalala points out. "We don't know about politicians, we are talking about homeless. Everybody is homeless, if not here, then before heaven.

"Music is like preaching," he adds. "All the time when you preach, you know that people will repent. There is loving songs to talk to people and tell them to forgive each other, to love each other as the Bible says, to love your neighbor. There are songs for making people happy. When people are happy, then everything will be okay.

"But I don't want to enter in other places, because I don't know about these things. I know only about singing and songs that are talking sense, that are uplifting, soothing. Then it's up to the one who listens to the songs."