It took years for "Walk the Line" to move from concept to shooting — film biographies were out of favor and studio after studio passed, sometimes twice, before 20th Century Fox gave the OK to the $28-million project. Phoenix used that time to immerse himself in Cash, both his recordings and books.

"His music was really the gateway for me to understand him as a person and to understand how he spoke," he says, slumped in his chair. "I'm talking about his actual records and demo tapes. What struck me early was that he didn't have a country accent at all. The key thing about him was the rhythm of his sentences."

The challenge, he says, is learning everything you can about the subject but not turning yourself over to him.

"When you start reading these books and listening to the tapes, there is a long distance between you and him, but the more you study him, the closer you get," he says. "The important thing once you get into the shooting of the film is that you never think about any of those things again.

"There was a period when I was very conscious of how John walked. He didn't bend his legs when he walked. He also had a certain posture. I tried walking consciously like him. At some point, however, all that has to become natural. If you are trying to remember to do it like John did, you probably aren't doing your job. It's when you get into that natural state that you really feel alive as an actor."

Mangold, who also wrote the script with Gill Dennis, insisted that Phoenix and Reese Witherspoon (playing wife June Carter Cash) do their own singing because he felt it would bring them closer to the characters.

After working with a vocal coach, they spent months in the studio recording the soundtrack album with T Bone Burnett, the rootsy musician who put together the music for "O Brother, Where Art Thou?".

Phoenix, who didn't even know how to play a guitar before getting the role, says he was terrified when Mangold asked him to sing.

"Even now, if you said, 'Here's a guitar, get up and sing a song for those people over there,' I couldn't do it," he says, gesturing to some patio diners. "I would … faint. But put me in a role and put those clothes on me and I'm absolutely able to do it."

THE ACTING GENE

PHOENIX may not feel comfortable singing, but he fell in love with acting at an early age. "I'm into exploring characters, exploring the human condition," he says, squinting from the afternoon sun. "I'm into psychoanalyzing people. I think it's something I grew up around."

He was one of five children in a hippie-styled, missionary family that traveled extensively during his early childhood before settling in Hollywood in the early '80s.

"In the early days, we were definitely poor," he says. "We didn't have video games or TV or any of those things. We barely had toys. So I think that forces you to rely on your imagination a great deal. You make up games and act out skits. We were encouraged to express ourselves. I don't recall ever being told to shut up when I was growing up."

He had a close relationship with his older brother, River, and followed him into acting, doing TV shows before breaking into movies. Even at the beginning, he had a sense of purpose as an actor.

"There was a point when I was around 14," he says. "I made a movie called 'Parenthood' with Steve Martin, and it was a big hit, and I noticed scripts started coming in and agents were suddenly calling all the time. But the scripts had no meaning for me. They didn't reflect what I thought was valuable or what I wanted to explore.