Amy Grant is Christian music's most celebrated and commercially successful artist, the first to achieve platinum status (with 1983's "Age to Age" album) and the first to break the 5 million mark (with 1991's "Heart in Motion").

About to turn 37, she's sold 20 million albums, won five Grammys and 26 Dove Awards, topped the pop charts (with the ebullient "Baby Baby"), had three kids, sustained a 15-year marriage with fellow Christian-country artist Gary Chapman (host of the Nashville Network's "Prime Time Country") and instituted a Nashville Christmas concert tradition that, for the first time this year, takes to the road. (Also featuring Michael W. Smith, CeCe Winans and the Nashville Symphony Orchestra, it arrives at USAirways Arena tonight for a 6 p.m. concert.)

Given all that, Grant was somewhat surprised three years ago when several people -- both close friends and professional associates -- told her they felt her music was not a full reflection of the person they knew and challenged her to explore her interior life, to go below the surface.

"I thought, especially on the heels of two pretty slick pop records, it was fair criticism," Grant says. "It wasn't like they were saying, What have you done for the last 14 records?' I think that people who knew me . . . felt it would do me good personally to dig around on the inside a little bit."

The result of what Grant has called "a complete self-examination from head to toe" is "Behind the Eyes," an album that moves away from the glossy pop sound of "Heart in Motion" and "House of Love" into uncluttered, mostly acoustic folk-rock constructs and somber texts. The album sits comfortably next to those by such singer-songwriters as Sarah McLachlan, Sheryl Crow and Shawn Colvin. On it, Grant meditates on loss of innocence, self-doubt, disappointment, darker adult emotions and introspective themes not generally associated with her past work.

"I love to sing Baby Baby' and I love pop music," Grant says. "I love Hanson -- I turn on the radio and my son, he's 10, rolls his eyes and goes, Oh, them again?' But you know what? I've got a need for that kind of music -- pristine, fun, pop music. {But making that kind of music} wasn't the most natural thing to me, but I was glad for the stretch.

"I think my natural tendency is a little more towards a folk sound."

Indeed, with her wavy sandy brown hair piled in a bun, jeans, leather jacket and acoustic guitar case, Grant looked more folk minstrel than pop star when she flew in last month for a solo performance at the Capital Women's Show in Fairfax County. .

"I am a somewhat unkempt person and earthy, always have been," she says with a laugh after doing a quick sound check with a Joni Mitchell tune. Growing up, Grant points out, her greatest influences were Mitchell, James Taylor, Carole King, Dan Fogelberg. Which explains why almost all of the songs on her new album are sung in the first person, even when they are the result of collaborations, including longtime songwriting partners Wayne Kirkpatrick and Tommy Sims (the latter a co-author, with Gordon Kennedy, of Eric Clapton's Grammy-winning "Change the World").

Grant and Kirkpatrick have written together for more than a decade, a partnership that begat friendship. "Seeing me at close range, Wayne started making some observations about me as a person, about the impact of a very public life, about some patterns in my life that I took for granted," Grant says, pointing out that she's been in the public eye since the age of 16.

"I don't think I had any idea what a profound impact that had on me," she says. "I think anybody, given their circumstances, assumes that what they experience is normal. You take a child in an abusive home and they go, This is my life.' You take somebody born with a silver spoon in their mouth, and it does not occur to them that people are living in lean-tos. Whatever it is that you wake up to and do every day, you just assume that's the norm."

That norm included the constant pressures of others' expectations and the stylistic and moral straitjackets of the genre. After all, Grant is one of contemporary Christian music's most visible figures, one who was criticized for making albums that crossed out of that market to the secular side, as if building a bridge meant abandoning long-held beliefs.

"There were times that it brought me to tears," Grant says, adding that she never felt she was being used "to work out somebody else's agenda. I always have been given freedom by Myrrh and A&M {which simultaneously release her albums in the Christian and pop markets} to follow whatever muse was in me.

"I think it's a very common experience for a woman in her mid-thirties to back away and say, I want to step back far enough from what I think is normal and value my life for what it is, reassess the investments that I've made, seek what's really good and what is really propped up. . . . It has nothing to do with God not being God anymore, or my need for Him, but how to process that information."

More so than her two pop-oriented albums, what's noticeable about "Behind the Eyes" is an absence of overt references to God or Jesus, though Grant's faith clearly informs the writing. That may lead to further criticism in the Christian market, but Grant feels confident in her position.

"The big hurdle I've finally gotten over is -- in a very healthy way -- that it doesn't matter to me anymore," she says of past pressures as the quintessential Christian girl-next-door-to-a-church. "It matters to me what I think, it matters to me what the people I have invested in think. That freedom from other people's expectations allows me to choose when and where to be vulnerable, to not be part of somebody else's agenda."

"Behind the Eyes" also represents a smaller-scale breakthrough: After 14 albums, this is the first one on which Grant plays guitar. She'd done so when she'd started out as a solo act at 15, but by the time she recorded her debut in 1978, more proficient players had assumed that duty. Grant's guitar gathered dust until three years ago, when, at the last moment, she included a cover of Joni Mitchell's "Big Yellow Taxi" on her "Heart in Motion" album.

As she traveled around the country on the concert trail, visiting radio stations, "people would say, Do "Big Yellow Taxi." ' And I thought: It's insane that I cannot play a song that has three chords! So I called Taylor Guitars and ordered a pretty one, and guys in the band kind of coaxed me through it. . . . Being forced to do something makes you be comfortable with it real fast."

Still, it was only a few months ago that Grant made her first concert appearance without a rhythm guitar player -- at a Billy Graham crusade. "The guys said, You know, you could have warmed up with something a little smaller than 90,000 people!' "

Her husband's recent ascendancy on the Nashville Network has brought another change to the family dynamic. There was a time when Gary Chapman would open for Grant on tour as he tried to forge a separate career; the year they were married was the same year Grant enjoyed the first of her nine platinum albums.

"The dynamic between us is that Gary loves the spotlight and I don't," Grant explains. "And the way the cards were dealt to us, I was given the spotlight even when I didn't want it, and he stood by and had to experience it being so close but not on him."

There were difficult times, Grant acknowledges, adding that "we've made a big shift in the last year because you can't get more public than a TV show, and he loves it. And the bigger the splash, the bigger the impact, the better for him, and I feel the heat is really off me."

Grant's two Christmas albums have sold more than 3 million copies and her Christmas show has been a Nashville tradition for several years, but this is the first road version (naturally, the 19-city tour will end in time for her to be home for Christmas). Grant will take to the road to support "Behind the Eyes," but not until after spring break, and probably in more intimate venues than her star stature warrants. It fits in with the introspective dynamic of the new material, as well as her new equanimity.

"I'm glad for where I am," Grant says firmly. "I wake up today and I have three children and that is a miracle -- I don't know how I squeezed three pregnancies in between records and tours.

"I'm married to someone who is very different than I am -- there are extreme dynamics -- and it has been many times a difficult situation, yet our home is still together. Well, there's another miracle.

"And I'm not insane -- another miracle!" CAPTION: Amy Grant will be performing at USAirways Arena tonight. CAPTION: Amy Grant takes up the guitar on her new pop albums.