But mostly, it's because I've always been fascinated by those people who can pull off the art of acting -- particularly on film, with its startling intimacy that gets the audience closer to faces onscreen than we usually do in real life except to those we are the very closest to -- and how when acting really works as an art and a craft it sets up a tantalizing duality that becomes about observing both the character and the actor. And it's because I must grovel at the feet of Joaquin Phoenix, with whom I've always been a little in love and to whom I now must pledge myself completely.

And this after, I am ashamed to say, I walked into the screening room thinking, Okay, Joaquin's cool and all, but Johnny Cash? I just didn't see how it could work. Then the "Johnny Cash" onscreen sang, and I did a mental double-take: Is that Cash's voice? Or is it Phoenix's? It sounds like the actor's, and yet, not. But it's his: no stunt-singers for Phoenix (Ladder 49, Hotel Rwanda), who sang every note live in front of the camera after never having sung before. He reached down real deep and brought up something from god knows where that's not quite an impersonation of Cash, nor a pastiche, but it's so much coarser and more darkly pitched and trill-ier than the actor's own voice that only some kind of wild actorly magic can be responsible for it. It's thrilling in a way that makes your toes curl, and it's so fucking amazing that you want to giggle with delight: how the hell did he do that? It is simultaneously Cash and not-Cash, Phoenix and not-Phoenix. And that's what I keep hearing on the CD, that beyond-intriguing duality, an almost tangible expression of the alchemy of The Movies contained in a few aching verses, a few rockabilly chords.

(Also: Reese Witherspoon [Just Like Heaven, Vanity Fair] is surpassing wonderful as love-of-his-life June Carter, not least because she does all her own singing, too.)

The finding-his-voice aspect to Phoenix's preparation for the role infuses what is perhaps the most magnificent scene in a magnificent film: Cash is auditioning for recording-studio owner Sam Phillips (Dallas Roberts) and it's going really badly until Cash reluctantly agrees to sing a song he wrote instead of the tired gospel tune he's been halfheartedly warbling. He starts out uncertain of his own songwriting talent and perhaps afraid of revealing the anger and bitterness that oozes from the song, but in one long uncut take, Phoenix takes Cash, as he performs "Folsom Prison Blues" for its first audience, from meekly tentative to aggressively confident, and the power of that transformation and the creative genius it took to make that work made the hair on the back of my neck stand up and turned my arms to gooseflesh. It makes me sorry for every time I ever called a performance "riveting" or "electrifying," because now, when I need words like that, I don't have them at my disposal -- I have cheapened them through careless use. But how could I have known I should have held them in reserve? I can't remember anything, onscreen or off, that actually made the hair on the back of my neck stand up. I think I thought that was just an expression -- I don't think I seriously believed the human body was capable of that.

Phoenix's transcendent performance is an extraordinary tribute to Cash and the might of his music, and would remind us of the impact Cash had on the course of rock 'n' roll even if the film on the whole didn't explicitly do so. We see perfectly well how Cash was in all ways the equals of Elvis Presley and Jerry Lee Lewis, not just musically but in the public imagination of the time. Director James Mangold -- working from Cash's books The Man in Black and Cash: An Autobiography and redeeming himself for his recent and dreadful Identity and Kate & Leopold -- wisely limits his film to Cash's early years rather than trying to cram in the man's entire life. Focusing on the 1950s and 60s, when Cash was touring with Presley and Lewis and other future legends, Walk the Line avoids the awkwardness of having to bury Phoenix under layers of latex as Cash ages beyond him, but more vitally, it leaves us with a Cash at the moment of perhaps his greatest jolt to pop culture: Mangold bookends his film with Cash's Folsom concert, and lets Phoenix's literally pitch-perfect "Hello, I'm Johnny Cash" reverberate in our minds as it does in history.

Tally: I listened to "I Walk the Line" 23 times while writing this review; "Ring of Fire," 18 times; "Folsom Prison Blues," 15 times. Help me.