The transformers of world music are back, writes Alexis Petridis.

It had been quite a morning for Joseph Shabalala and Ladysmith Black Mambazo. They were in Amsterdam to record a track with a Dutch artist. Shabalala describes the experience as "very, very nice and easy". It's doubtful any other artist would share this view. Shabalala had written a new song for the occasion, a fact he neglected to mention to the other members of South Africa's most successful musical export until they arrived at the studio. "I don't tell them," he explains, "because I don't want them to get frustrated." But weren't they frustrated when they discovered they had to learn and record a new song before lunch? "No, no, no. I can talk to them very nicely, and they can catch it."

Shabalala, who is 63, indeed talks very nicely. His speech shares some of the qualities of his remarkable singing voice, which he demonstrates by breaking into song. There is usually something embarrassing and self-indulgent about pop stars singing at you while you're trying to interview them. When Shabalala does it, you just sit and gawp. His voice is high, quivering and mournful. When he talks his voice is gentle and lulling, even when he discusses the past 12 months.

Shabalala's 2002 seems bizarre and shocking. First, his daughter died of AIDS. Then his wife, Nellie, was murdered in front of him. Then his 42-year-old son, Nkosinathi, was arrested and accused of plotting his stepmother's death. The charges were dropped and a hit man is now due to stand trial for her murder.

Perhaps surprisingly, days after his wife's murder Shabalala was back on stage, performing in London at the Party at the Palace concert. "I wanted to," says Shabalala. "All the time I was thinking maybe I'm going to wake up, but when we sing the music gives me more power. It was like it was OK, I can carry on. When I'm on stage, I feel like she's there. When I sing the song Hello My Dear, it is just like I'm greeting her." Eyebrows were further raised by his decision to remarry six months after his wife's murder, to a local charity worker "brought to me by God in a dream".

There is a sense that Shabalala views recent events as yet another twist in a life of extraordinary incidents. The son of a farmer, he claims that Ladysmith Black Mambazo's unique variation on Zulu isicathamiya singing also came to him in a dream, while he was a mechanic in 1960s Durban. It took him four years to assemble a group capable of achieving the sound. By the early 1970s, their music had crossed over to a white audience, a remarkable feat in apartheid-era South Africa. Ten years later, they began performing in Europe and the US. Famously, their collaboration with Paul Simon on the 1986 album Graceland took them to an enormous global audience.

Almost 20 years on, Ladysmith Black Mambazo remain in a very uncommon position. They and the aged vocalists of Cuba's Buena Vista Social Club are the only artists to have crossed over from world music into genuine global success. World music is still seen as the province of the terminally worthy. Yet we make an exception for Black Mambazo.

But there is also the faintly troubling sense that in the West their harmonies have become a musical shorthand for the dignity of the oppressed. When Western artists want to add a touch of meaningful exoticism to their records, Shabalala gets the calls. Advertisers, too, have made the connection. The band's popularity in England was revived by an advert for baked beans, and their music has shifted everything from Seven-Up to IBM computers. He says the adverts and guest appearances all serve a greater purpose in promoting the Zulu culture - not to Western audiences but to other Zulus.

"When I first get the guys together, I say to them, our people are scattered, they lost hope, we must take this sound somewhere and tell them. All the schools are teaching Zulu music now, and that only started after the big tour with Paul Simon. The children come back home after school and say they hear Black Mambazo and ask, is this our culture? This is beautiful, we listen to it at school. Before, if they come back with books, what is the grandfather going to say? He doesn't know anything about books. But now, he can tell them, it's from this music, you find it in the wedding songs, in the Zulu dances. At last they have their culture. That's wonderful to me." He sighs. "I think I'm going to die in peace."

Ladysmith Black Mambazo are at the Helix, Dublin, Thu and Fri, UCH, Limerick, Sat, and Cork Opera House, Sun