There's a good reason Mare Winningham is able to convincingly play six very different women in the Atlantic Theater Company's new musical Ten Million Miles—she has a wide range of experiences from her own eclectic life and career to tap into. The 48-year-old actress' personal journey includes attending high school with Kevin Spacey, having four kids beginning in her early 20s, a stint with the Brat Pack (St. Elmo's Fire), an Oscar nomination (Georgia), two Emmy Awards (Amber Waves, George Wallace), three CDs as a singer/songwriter, memorable guest appearances on hit TV shows (Grey's Anatomy, ER) and a midlife turn to religion. Now she can add an off-Broadway musical to the list. Set to songs by folk artist Patty Griffin, with a book by Keith Bunin, 10 Million Miles follows a young couple named Duane (Matthew Morrison) and Molly (Irene Molloy) on a not-so-smooth road trip up the East Coast. Along the way, they encounter Winningham as an elderly factory worker, a worn down mother and an inebriated bride-to-be, among other roles. Though she appears onstage sporadically, Winningham manages—sometimes with just a few lines of dialogue—to imbue her characters with a rich inner life that makes them fully realized creations. During previews, the native Los Angeleno took time to chat about her New York stage debut and the winding path she took to get here.

You've done just about everything—stage, film, television, music. What made you decide now was the time to do a musical?
My youngest kid went to college [laughs]. Since I was a young girl, I've wanted to do a play in New York, but it just wasn't possible with the family. It was actually really calculated, though. When I was 21, I added up how old I would be when I had the last one, because I had them all very close together, and I thought, "Oh, I'll be a ripe middle-aged women; it might be right to go to New York and do a play." [Laughs.] It felt like a little shining star when I got the call about the audition because it was right on cue. The 18-year-old goes to college, and six months later Mom gets the chance to do a show.

Were you familiar with the Atlantic Theater before you got the call to audition?
I'm friends with Felicity Huffman and [Atlantic co-founder] Bill Macy, so I had met a lot of the Atlantic people at a birthday of Felicity's. I had seen some shows there, and it seemed like a real actor-y company. I love their choices. If I had made a wish list, it would have been to do a play in New York as soon as the kids grew up, have it be at the Atlantic—and why not have it be a musical with Patty Griffin songs?

Were you familiar with Patty Griffin's music?
I was. I came to her the way I think a lot of people do, which is that I'm a big Emmylou Harris fan and Emmylou records a lot of Patty's songs. Patty's voice is just magnificent, but also there are incredible stories in every song. She can be a homeless guy pacing on a street or an old factory worker making pies or somebody broken or somebody determined, but there's always a central character singing the song. They're unforgettable when you hear them in concert. I wonder if [book writer] Keith [Bunin] had that same experience, of going to her shows and getting swept into her world.

Have you gotten to meet her while working on the show?
Yes. When we met her, it was a little silly; everyone was so in awe of her. We had been working on the songs for a month, and the more you work on them the more you discover they are mysteriously powerful. By the time she showed up at rehearsal, nobody really knew what to say. [Director] Michael [Mayer] was very funny that day. He's a funny guy anyway, but he was hysterical that day; he broke the ice and made her laugh. It went really well. The following night we all went to see her at The Beacon, which was amazing. It was another great perk of this whole thing.

You've done plays before, but never a musical. How are you finding the experience?
I didn't know that you get a month of previews! I didn't know that there were six weeks of rehearsal, and that the first previews are like you're trying it out, like you're in Cincinnati or something. Huge changes took place during previews, all for the better. I mean, major rewrites. And that is apparently what they expect. The audience informs you; it becomes this play between the songs and the show and the audience.

Are you finding that process rewarding?
Very. And it's making me feel like I was a little bit of a Negative Nellie at first, because I just didn't know what was in store. They [Mayer and Bunin] knew that's how you find out where to push and where to pull back. I learned a big lesson. I think back to the phone calls I made home during the first week of previews that were like, "Well, we're doing our best." Now I think there is a real show there.

Does doing that kind of work bond you as a cast?
That actually happened pretty early. Most of the first week was just the music director and the four of us [Winningham and co-stars Morrison, Molloy, and Skipp Sudduth]. It was a very nice way to start, because we all love singing, and we were sitting around learning harmonies. It was built-in fun, like a campfire! We laughed all day. I look back on that as my favorite week—not that it's been downhill, but that we could bond like that.