He's been challenge, and Jack White doesn't back away from a challenge -- especially when it involves his electric guitar. He straddles a metal chair in a dingy room on his Nashville farm, grips a pencil in one hand and a tattered notebook in the other, then goes to work.

A camera follows White's every scribble, the guitar pick clenched between his teeth, the strands of black hair obscuring his face, while director Davis Guggenheim waits patiently to see if the White Stripes frontman can pass this rock-and-roll test.

"I said to Jack, 'You believe in writing songs fast, that music is over-produced. Write a song now on camera!' " Guggenheim told MTV News.

Not only did White write and record a song in less than 10 minutes, but the entire process became a living, breathing, guitar-shredding example of the point Guggenheim's documentary, [article id="1617764"]"It Might Get Loud,"[/article] is trying to make clear: The very best artists make an inextricable connection between emotion, songwriting, expression and music so good you feel it in your bones.

"Get Loud" focuses on White, Led Zeppelin's Jimmy Page and U2's the Edge as they come together to jam and split off back to their days of songwriting and everyday living. MTV News has obtained the footage of White's musical challenge days before the doc comes to theaters Friday. White is no doubt proud of his speedy work, too, as the track, called "Fly Farm Blues," was available for purchase on iTunes starting Tuesday.

As White explains in the documentary, "If you don't have a struggle already inside of you or around you, you have to make one up. Something that made you angry or upset or jealous."

After sketching out the lyrics to "Fly Farm" in pencil, he switches on his old-school reel-to-reel recorder -- saying with a shrug, "OK, let's see" -- leans into the mic, and begins to play a stripped-down blues progression.

"Spider got eight legs/ I got two," he sings. "This guitar got six strings/ But what about you?/ Yeah, what do you got?"

At the end, he puts the guitar down and rewinds the tape, bringing everything to a close as quickly as it started. It's hard to tell if White is merely playing it cool because he knows he just popped off a kick-ass tune, if the perfectionist inside him is even happy with the work, or if he's regretting accepting the filmmaker's challenge. But then he hands the tape over to Guggenheim. Jack White clearly knows he's pulled off a winner and all he has to do is say -- again with a rock-star shrug -- "That's it."

Check out everything we've got on "It Might Get Loud."

For breaking news, celebrity columns, humor and more -- updated around the clock -- visit MTVMoviesBlog.com.