Ladysmith Black Mambazo
"Long Walk to Freedom" (Heads Up International)

Ladysmith Black Mambazo stepped into the classical realm for its collaboration with members of the English Chamber Orchestra on last year's No Boundaries, but the South African singers tiptoe into their own past on these 13 songs.

Long Walk to Freedom is timed to celebrate the 20th anniversary of Ladysmith Black Mambazo's famous collaboration with Paul Simon on his landmark Graceland album. It put South African music into the consciousness of a pop audience and lifted Mambazo from relative obscurity.

To mark the occasion, the ensemble's founder and signature personality, Joseph Shabalala, has assembled an impressive list of guest artists to help reinterpret music from all phases of Mambazo's career, which stretches back to the early 1960s.

Graceland is referenced in new versions of the frisky "Diamonds on the Soles of her Shoes" and a tender a cappella "Homeless."

The former features Melissa Etheridge on lead vocals that radiate a harder edge than Simon's original. Her presence sounds a little odd at first, until the song is carried away by the exuberant backing chorus that injects the melody with new vigor. A big part of the appeal is human beat-box Joe McBride, who adds the essential percussion.

Sarah McLachlan joins the singers on "Homeless," which otherwise doesn't stray too far from the delicate original, including Shabalala's tremulous, almost whispered, falsetto introduction. Compared with the subtle power of the ensemble, McLachlan's contribution is almost invisible.

Natalie Merchant establishes herself more naturally on "Rain Rain Beautiful Rain," an incantation culled from Mambazo's 1987 Grammy-winning Shaka Zulu. The soft, simple tune sounds like a sweet lullaby, a mood reinforced by Merchant's understated delivery.

Mambazo, of course, doesn't need pop stars to shine. The distinctive blend of voices, deep and gentle, is like a force of nature on the opening "Nomathemba" and the gospel-tinged "How Long."

So whether it's bluesman Taj Mahal adding exhortations and electric guitar to the familiar chorus of "Mbube" or Emmylou Harris going country on "Amazing Grace" and "Nearer My God to Thee," it's the raw voices of Mambazo that make "Long Walk to Freedom" worth the trip.