They call it isicathamiya.

The a cappella form's rumbling drones, keening ululations and breathy, puffing stomps are as much a part of the South African musical landscape as the shouts, harmonies and choral responses of gospel music are of the American South.

Albert Mazibuko began singing isicathamiya as child, long before he joined Joseph Shabalala in the visionary group Ladysmith Black Mambazo, which returns on Sunday to the Troy Music Hall.

"I grew up in a musical environment where people are singing while they're working," Mazibuko says. "We sing if we are sad. We sing if we are happy. Music has a very vital role to play in our lives."

He says children still learn to sing isicathamiya in contemporary South Africa.

"People get together every Saturday evening to sing in many areas," Mazibuko says. "And the young people today are even more involved in it, because in the schools they have a competition that is sponsored by the government."

Shabalala formed Ladysmith Black Mambazo in 1974, but it was the group's appearance on Paul Simon's landmark 1986 album "Graceland" that brought it to the attention of the rest of the world.

Shabalala gave his 10-man ensemble a name that would make rappers proud. Ladysmith is the name of Shabalala's rural Zulu hometown; "black" is a reference to oxen, the strongest of the local animals; and mambazo is the Zulu word for ax, a symbol of the group's ability to chop down any singing rival that might come its way.

But the gifted singer didn't want to populate the region with just one more cadre of strutting tunesmiths. Shabalala, an ordained minister, converted to Christianity in the late 1950s, and used Ladysmith to merge the vocal traditions of isicathamiya and gospel. The fusion was passionate, spiritual and immediately identifiable.

In its essence, Ladysmith's style has changed little, although the landscape has changed a great deal.

Singing with Simon made the men in Ladysmith famous, and it set them off on a continuing series of world tours. More importantly, in the mid-'90s the apartheid system in South Africa finally fell.

Mazibuko says the current tour is, in part, a celebration of the 10th anniversary of the end of apartheid. He feels Ladysmith played a positive part in the political upheaval.

"Our music is about inspiration," he says. "It's uplifting. It's meant to encourage people to do the best they can with what they've got, to use their talents, god-given talents."

"I have been told by freedom fighters, political prisoners and exiled citizens that our music was an inspiration to them. They said our songs gave them the strength and hope to carry on with their efforts. It has always been our aim to empower the black people to stand up and believe in themselves ... and to achieve great things."

The group's latest album, "Raise Your Spirit Higher -- Wenyukela," includes several songs that are literally pleas to invest in Africa.

"Things are very different in South Africa now," Mazibuko says. "We've got our freedom now, so we invite people from all over the world to visit us, to work with us, to stay with us.

"` ... We also have songs that encourage people at home to get up and do things for themselves, because the opportunities are now open to them."

"Wenyukela" is the first collection of original Ladysmith music to appear in America since 1997.

Mazibuko says that at home the group has released a number of straight-up isicathamiya releases over the past few years, strictly for the South African audience.

He also points out another reason for the delay. In the spring of 2002, Shabalala's wife of 30 years was murdered in a church parking lot by a masked gunman. The killing is still unsolved. ("There are some people who are being questioned right now," Mazibuko says, "and there may be some sort of a trial next month.")

The new album track "Tribute," penned by Shabalala's teenage grandsons, is a brief hip-hop paean to their lost grandmother.

"Joseph is doing very well, and we pray for him every day," Mazibuko says. "And when we have time out on the road we also get together with him and pray, because we know that prayer is the only thing that's going to keep him up and carrying on with the music."

At the Troy show, Ladysmith will be joined by the Ugandan performer Samite, who is now based in Ithaca. Like Ladysmith, Samite creates a blend of ancient and modern sounds, using traditional Ugandan instruments and modern technology.

Shabalala has said of Samite, "When you hear his music, the soul of Africa is revealed."