TORONTO – Four years ago, we talked to Joaquin Phoenix in a Toronto hotel room much like the one he occupied at September’s 2005 Toronto International Film Festival. After hellos, he politely asked permission to smoke. Over the next 40 minutes, Phoenix smoked three cigarettes, and his left leg never stopped jittering. As articulate as he might have been, his body language was that of someone being questioned about a crime he didn’t know if he had committed.

This time, Phoenix, 31, still asks if it’s OK to smoke, but at the end of the conversation, only one butt is in the ashtray. He is looking relaxed and speaking confidently, like someone who knows he has done justice to a bona fide legend.

In director James Mangold’s “Walk the Line,” opening Friday, Phoenix plays Johnny Cash, a man whose face, style and voice is familiar even to those with an aversion to country music. The film focuses on the tumultuous relationship between Cash and the woman who would be his wife, June Carter, played by Reese Witherspoon. Though Phoenix pursued a part that many actors coveted, he admits to being a “little panicked” when he was told he had won the job.

“I thought, ‘Oh, this great!’ followed by, ‘Oh, I don’t know if I can do this.’ The truth is, I was an admirer of Johnny Cash the man, but I really wasn’t familiar with his work,” Phoenix said.

He first talked to Mangold, director of the gritty thriller “Copland,” around the time he was getting his first mass exposure in his supporting role in “Gladiator.”

“My girlfriend of the time, Liv Tyler, knew Jim and had told him she thought I might be right for the part, I’m not exactly sure why. Anyway, we had a good talk, but I told him upfront I wasn’t a musician or a singer. At that time, it hadn’t been decided if we would actually perform the music or use Johnny’s original recordings.

“Still, the first thing I did was go out and buy a guitar and just learn how to hold it, you know? I got a book and taught myself a few chords. But I didn’t do any research really, because I thought if I did, I’d jinx it. So when the film finally did get a green light, I had some cramming to do.”

Reactions to “Walk the Line” following its Toronto premiere were mixed, but one thing nearly everyone agreed on was the strength of the performances by Phoenix and Witherspoon and the chemistry between them.

“I don’t know that I could have done this without Reese,” says Phoenix. “We have very different acting styles, but she had enough faith in our compatibility for the both of us. She’s the one who got me a singing coach and hooked me up with T-Bone (Burnett, the producer and guitarist best-known as the man behind the multi million-selling “O Brother Where Art Thou” soundtrack), who was really encouraging.

“But I think the first time I felt like it was going to be OK was when Johnny’s son John R. came to a rehearsal,” he says. The younger Cash was a consultant on the film, and acted as a go-between for the producers and his then-ailing father.

“He said, ‘You know, you hold that guitar just like Daddy did.’ That was enough to keep me going.”

Witherspoon, interviewed later from Los Angeles, was also intimidated by playing someone so well-known. She grew up in Nashville where, she says, “country music was everywhere. The voice of Johnny Cash was everywhere.

“I had never played any real-life characters in any of my films, and I realized pretty quickly there was a responsibility attached. You want to be true to who these people were, but you also have to have their trust. Remember, John and June were both still alive when James started working on this almost 10 years ago, and they were very concerned about how they would be portrayed.”

Though Cash and Carter had written and talked extensively about their relationship – which began when June was still performing as a member of the legendary Carter Family singing group and Cash was an up-and-coming young country star appearing at the Grand Ole Opry – they had always said their relationship was never physical while both were married to other people.

“Nobody really believed that, but these were Christian people with families who grew up in a time and place where adultery was considered a truly sinful act, not some sort of casual thing that was easily forgotten or forgiven,” says Witherspoon, whose company produced the film.

“Finally, Jim just told them he couldn’t make the movie and make it convincing if he tried to maintain that fiction, because the truth was, what they had done weighed heavily on them; it affected how they lived. Ultimately, they said OK, but it was hard for them.”

Witherspoon said that the idea of doing the actual performing in the film initially “scared me to death. The only public singing I had ever done was as a kid, in plays, that sort of thing.”

But it was eventually decided that unlike “Ray,” the Ray Charles biography with which “Walk the Line” is destined to be endlessly compared, the actors would do their own singing.

“I actually had it easier than Joaquin because while June had a beautiful voice, the focus was never on that in the early years; her sisters were always considered the real singers. She mostly contributed harmonies.”

It was decided that Phoenix would try to find the essence of Cash’s distinctive unvarnished baritone and not attempt an imitation.

“I couldn’t go out there and say, ‘Hello, I’m Johnny Cash’ and then have a voice come out that sounded like some punk rocker or something,” says Phoenix. “James just kept reminding me that if people wanted to hear the actual voice of Johnny Cash, they should buy the records. That took some of the weight off.”

Phoenix met the Cashes only once, at a dinner party in Los Angeles, before they died in 2003. “What I mostly remember is being a little in awe, and them making me feel comfortable,” says Phoenix. He researched his role by reading Cash’s two autobiographies, listening to “some pretty wild-ass stories from members of his family and people who knew him,” and watching film of Cash performing and being interviewed.

“Walk the Line” ends in 1968, with Cash’s historic and defiant performance at Folsom Prison, before he had a weekly TV show and became a national icon.

“I wanted this to be authentic as possible, but I also wanted to play the people, not the images,” says director Mangold. “The Johnny and June you see in this movie are the people outsiders never saw.”

Still, the only time Phoenix bristles is when asked whether the stories were true that he did a Daniel Day Lewis on the set, remaining in character throughout the shoot and only responding when addressed as John or Johnny.

“I don’t even know what method acting is actually,” he says. “What I know is what works for me, what feels comfortable and right. And if I’m constantly switching between the character I’m playing, losing his walk or speech and joking around with my friends between set ups, it takes me out of the work. So, no, I don’t like hearing somebody on the crew yell, ‘Hey Joaquin,’ or doing an interview when I’m working. The thing is, it’s embarrassing to talk about now, when it’s over, but at the time, it feels right. Some films, I might not go that way, and I might try something differently at another point in my life. But for now, this works for me.”

On reports that her and Phoenix’s acting styles and personalities clashed during filming, Witherspoon is diplomatic.

“We all have different ways of working, and after you make enough movies, you learn to accept that people have to go where they have to go to get the best from themselves. I can tell you that any disagreements any of us had were always about making the movie better, about honoring the story,” she says.

“I’ll tell you this about Joaquin,” says John Travolta, who played Phoenix’s fire captain mentor in the smoke-eaters drama “Ladder 49.” “I don’t think he took one breath in that movie he didn’t believe. This is one very commit
ted young actor. I looked at him and wished I had always been that dedicated when I was his age.”

After a five-month rehearsal period and four months shooting the film in Nashville and Mississippi (during which time the stars also recorded their vocals), Phoenix admits it took him a while to find himself again. “There would have been no way I could have just jumped into another movie.”

Besides, he says, he had done three movies “pretty much back-to-back” before plunging into “Walk the Line. ”

“I definitely needed some time off, but when we were done” – with “Walk the Line” – “I didn’t know what to do with myself. I felt like I was separated from that reality for a long time. Plus, I was really anxious about what Johnny and June’s children would think. That was the review that I really needed to hear.”

Phoenix says his reward was shaking John R. Cash’s hand after the family’s private screening, and getting the verdict.

“I think a lot of this might have been hard for him and my mother to watch if they were still here, but I truly think he would have been proud,” says Cash. “The thing he cared about the most, in his music and his life, was being truthful. And I believe he’d say it got to the truth.”