That was the revelation of Friday night's Ladysmith Black Mambazo concert at Sanders Theatre. At the end of a snowy day, Shabalala's 10-man South African a cappella group promptly melted the sold-out crowd.

The singers jogged onstage, waving and jumping like an Olympic track team warming up in leopard-print dashikis. Then they launched into the title track from their new CD, "Raise Your Spirit Higher (Wenyukela)."

It was an invocation. Shabalala, who founded the Grammy-winning group four decades ago, began a call and response. Deep, rich harmonies filled the hall. Then Ladysmith began to dance.

If you know these guys just as backup singers for Paul Simon on his "Graceland" album, you may not be aware of the extent of their goofiness. There was a lot of clowning -- the kind of shtick that makes 5-year-olds (or 50-year-olds) anywhere laugh. Shabalala has brought four sons into the group, and they mimed, waggled their butts, blew kisses, and pretended to fight at various points. Between tunes, the singers joked about traveling so much they didn't know where they were: "Is this Boston Chicken?"

Many of the numbers were soothingly repetitive, with gentle melodies, soft harmonies, and the rhythm of a casual walk around the block. But the dancing looked anything but casual: intricate steps, stomps, hand flutters, chops, waves, and high kicks, all while singing. Imagine the five-man Temptations, multiply by two, and add Zulu lyrics, and you get the idea.

Some of their songs were lighthearted, while others had serious themes: missing their native land, or the difficult transition from apartheid to democracy. When Shabalala, who is a Christian minister, introduced a song about homelessness, some fans recognized it and began to clap. For a moment, we faced the embarrassing prospect of Cantabrigians in the good seats singing along in a heartfelt chorus of "We are homeless." Thankfully, it dissipated.

Ladysmith has come a long way since South Africa's darkest days. With music derived from the traditional songs of poor black miners, it has performed for Queen Elizabeth, the Pope, and a Broadway show. It has sold millions of records and become a nation's cultural emissary.

Sometimes, the weight of it all made the evening feel earnest, a little solemn. But then suddenly someone would shimmy, a leg would kick out sideways, grins would break out across the stage, and they were off again. It was as if they were saying they loved to let themselves go, but they never forgot where they came from. And that's the gospel truth.