NASHVILLE -- The crowd was dancing as soon as the bluegrass trio Nickel Creek went on stage, with hot-shot mandolinist Chris Thile careening around like a possessed marionette.

The opening number "When in Rome" was an edgy tale about lost souls trapped in a cold world where the doctors can't heal, people burn books for heat and no one answers distress signals. By the time Thile reached the apocalyptic last verse, he was raising questions about life, death and life after death.

"Where can a dead man go? The question with an answer only dead men know," he sang, briefly frozen in a stark white spotlight. "But I'm going to bet they never really feel at home, if they spent a lifetime learning how to live in Rome."

The crowd rocked on. There were tattooed youngsters in the aisles, dancing next to hip home-schooling parents with their children. There were bluegrass purists offering whoops of praise, sitting near some NASCAR fans wearing Birkenstock scandals.

The Nickel Creek crew -- guitarist Sean Watkins and his sister Sara on fiddle, along with Thile -- are hard to label and so are their fans. One reason for that is the band's Grammy Award-winning fusion of bluegrass roots with rock attitude. Nickel Creek often veers from Bill Monroe traditionalism to MTV Nirvana without blinking, with stops in John Coltrane and Beach Boy territory along the way.

But there was another reason the crowd in War Memorial Auditorium was unusually diverse. Nickel Creek offers a unique mix of old faith and modern doubts.

The trio has been together 16 years, beginning as children in devout Christian homes in San Diego. Early on, they recorded a gospel-bluegrass album called "Here to There" before heading into the mainstream with the help of superstar Alison Krauss.

It's crucial that bluegrass is one form of music in which artists are allowed to sing about Sunday morning as well as Saturday night. Thus, the members of Nickel Creek have been candid about their beliefs, while staying light years away from the prison called "Contemporary Christian Music."

Faith isn't an artistic curse if it stays honest, said Sean Watkins, who has written most of the trio's songs that wrestle with religious issues. It's interesting that old hymns are often more candid and searching than today's gospel pop songs.

"I'm so sick of sugar-coated songs from the Christian perspective," he said, in his online journal. "One of the most comforting and inspiring lines to me is from the last chorus of 'Come Thou Fount' where it says, 'Prone to wander, Lord I feel it. Prone to leave the God I love.' Not many un-watered-down songs make it through the filter of the Christian music industry mafia these days."

But honesty is a two-edged sword.

That's why Thile -- at the ripe old age of 24 -- was standing in a harsh spotlight singing songs about death, despair and divorce. One of his new songs is called "Doubting Thomas" and includes these poignant lines: "Can I be used to help others find truth, when I'm scared I'll find proof that it's a lie? ... I'm a doubting Thomas. I'll take your promise, though I know nothing's safe. Oh me of little faith."

Thile said he hopes to live his life as if death is not the end, struggling to "keep one foot in this world while sticking one foot out of it, just to get ready." At the same time, it's hard to avoid the kind of burned-out, shopping-mall confusion that leads so many young people to feel alone and disconnected, even while they crave relationships that will last.

Thus, this Nickel Creek concert closed with the trio sharing one microphone, gently singing this lullaby: "Why should the fire die? My mom and dad kept theirs alive."

"We are tempted to distance ourselves from the things that are truly powerful and beautiful in life," said Thile. "Faith is certainly one of those things. Faith is huge, and so are friendships and our family relationships. ...

"Anything that is truly worthwhile is both powerful and dangerous at the same time. Anything that is truly beautiful and lovely can also turn twisted and ugly. But we can't hide from all of that. That's what is real."