Musical diversity is the pulse of Africa

"I remember when we first lived in Toronto, Somalis would move to the ghettos . . . so they could save money and send it back home," said K'Naan, who emigrated at 12 and lived in several U.S. cities before settling in Canada. "People congratulate you when you get public housing -- because you finally get to send money back. So the kids, they just have their Wal-Mart sneakers or whatever, and other kids say, 'Man, you must be a real loser.' That Somali kid, you're judging him by his shoes, but leave the guy alone. That kid was a militia leader back home. He's been firing a gun since he was 7. That is the thing that I try to unveil."

K'Naan's border-crossing style also allows him to reach across musical genres. Some tracks on "Troubadour" reflect the influence of rappers such as Chubb Rock, who guests on one track, and Q-Tip. Others highlight K'Naan's connection to the first family of reggae; he recorded the album at Bob Marley's Tuff Gong Studios and the late Jamaican legend's sons Damian and Stephen are his good friends. As for pop crossover -- besides that rare guest turn by Hammett -- blue-eyed soul man Adam Levine pops up.

"In K'Naan, we saw a hybrid of musical styles," said James Diener, CEO and president of Octone Records. "There's an African hip-hop component, but what distinguished him were the elements of reggae and world music, and most interestingly, his sense of melody and his pop aesthetic. This album has incredibly commercial appeal."

Amadou & Mariam have exhibited a similar ability to not simply cross but seemingly erase musical boundaries. The pair met as students at Mali's Institute for the Young Blind and made several more traditional albums before pairing with the polyglot Basque-Galician producer Manu Chao for "Dimanche a Bamako."

Amadou & Mariam's U.S. label, Nonesuch, is a leading force in world music. Cuba's Buena Vista Social Club, Brazil's Caetano Veloso and African stars N'Dour and Sangare are a few of the many artists who license or release work through the label. But "Dimanche a Bamako" represented a breakthrough, said David Bither, a label senior vice president.

"Of all the African records we've released, I've never given a record to more people who came back and said, 'This is incredible,' " he said. "That was something we heard in that right away. It was crossing stylistic boundaries, international boundaries, all kinds. It was so fresh."