It's not just another biopic.

This weekend's new movie "Walk the Line," which chronicles "Man in Black" Johnny Cash's life from childhood to his rise to fame in Memphis, is garnering critical acclaim and strong Oscar buzz for Joaquin Phoenix, who plays the country music icon, and Reese Witherspoon, who plays his wife, June Carter Cash.

"Johnny Cash's story is incredibly inspiring, how he came off a cotton field in Arkansas and became this man who fulfilled his dreams," Witherspoon told FOX News.

"He wasn't trendy. That to me is what I respond to in his music. You know, I think that you listen to John's songs and you feel like you're in a room with him alone, and he's just telling you this story," Phoenix added.

And learning to sing wasn't a natural transition for either of the two stars, who took months to perfect their voices and conquer any stage fright.

"I had to learn how to sing. I actually, I was lucky because Joaquin was there the whole time, going, 'How can I do this?' And I was like, 'I don't know. Are we just stupid? Is this stupid?' And we just sort of coached each other, and supported each other and helped each other through the process," Witherspoon said.

"There was a point, working with the band, that I started just really playing the songs, and enjoying playing the songs, and I wasn't worrying about how I'm holding the guitar, and I wasn't thinking about the chords, and I wasn't thinking about my voice. We just were playing and singing, and that was just an amazing experience," Phoenix added.

AP movie critic Christy Lemire says: "Together and separately, Phoenix and Witherspoon elevate 'Walk the Line' above what it essentially is: a conventional biopic.

"The title is 'Walk the Line' because the film is about Johnny Cash, whom Joaquin Phoenix plays with a raw intensity and a blaze in his eyes that's part bad boy, part scared child, but 100 percent emotional commitment. Then along comes Reese Witherspoon as Cash's lifelong love, June Carter, and she pretty much steals the movie right out from underneath him.

"This is in no way intended to disparage Phoenix's performance. What he has done in capturing the energy and essence of a towering American cultural figure, without lapsing into facile imitation, is nothing short of extraordinary, especially when you consider that's him singing and playing the guitar in Cash's deep, driving style.

"Witherspoon, though, just takes over the entire screen, and when she's gone you want her to come back (sort of the way Johnny himself felt about June as they pined for each other while married to other people). ... June Carter is the part she was born to play, allowing her to showcase her radiance and charm and also her maturity. ... They should just give her the Oscar now and get it over with."

FOX News' Mike Waco and William LaJeunesse contributed to this report.