When Josh Groban began work on his third CD, the multiplatinum artist "knew that I had to go where my heart and mind were telling me to go, even if it would be a risk," he says. "Not taking the risk would have been the bigger risk."

That's how Groban, 25, sums up the strategy behind "Awake," released this week. The classically trained singer, whose robust, creamy baritone and smoothly sweeping ballads have made him a fixture on adult-contemporary radio, "wanted to put myself in situations where I was thrown into the fire a little bit."

To help him make that leap, Groban enlisted an eclectic group of collaborators, among them Dave Matthews, Herbie Hancock, electronica chanteuse Imogen Heap and the celebrated South African group Ladysmith Black Mambazo.

Groban's longtime champion David Foster also is on board, along with other celebrity producers such as Glen Ballard and Marius DeVries, both known for slightly edgier mainstream pop.

Foster embraced Groban's decision to broaden his horizons.

"He and I both agreed that it was time to try some new things and was much more involved with the mixing and the mastering," says Groban, who also co-wrote several songs.

He describes the results more as an evolution than a departure. "It's the perfect combination of what I feel I'll always do and what I hadn't yet tapped into."

The tracks that fall more into the latter category could pose a challenge, Groban concedes. "The more open-voiced, classically inspired music on this album was kind of a no-brainer. I would go in the front of the microphone and it would just come out."

Other tunes set off what Groban describes, half-jokingly, as "a battle between my voice and my brain. Your brain is telling you, 'This is the style of music that inspires you.' And your voice is going, 'No, no, no — I have to sing like this.' "

Groban has explored new terrain outside the studio, too. His last tour included performances in South Africa, a place he had dreamed of visiting for 15 years, since his parents bought him a copy of Paul Simon's "Graceland," which also featured Ladysmith Black Mambazo.

"I started learning more about what was going on in that part of the world, the music and the culture, and apartheid. I read Nelson Mandela's autobiography."

The singer got the opportunity to visit Mandela when he was made an ambassador to the civil rights champion's organization 46664, which addresses issues such as AIDS awareness and global poverty.

"You don't really say much when you're with (Mandela); you sit and listen," Groban says. "The whole time I was thinking, 'Please, please, please don't let me forget how I feel right at this moment.' It was so inspiring."

Groban exudes a similar sense of boyish humility even when he's not discussing international heroes.

His is not the persona of a larger-than-life pop star, he admits. "There are many times when I really think that nobody knows who I am," Groban says. "If people come up to me on the street and ask for a picture or an autograph, they just say, 'Thanks for the music.' Actually, I feel lucky for that, because I'm able to have a private life."

Not that he'll have much time for one any time soon. "I'm going back on tour, and there will be a lot going on between that and the foundation and a few other things."

His long-term goals include Broadway.

"I've always loved theater. And growing up, I felt like my voice was most suited for it," says Groban.

"It's going to be a very busy couple of years. But as much as I may complain about the stress or how I never have time to see anyone, I wouldn't have it any other way."