When Led Zeppelin’s Jimmy Page talks excitedly about “the whole aroma of it!,” you might think of wine, women, or weed. But the senior statesman of strum is, in fact, speaking of something far more precious: his ax. Page is part of a troika of guitarists, including U2’s The Edge and The White Stripes’ Jack White, who spend the better part of the documentary It Might Get Loud talking about how much they love their guitars. And, boy, do they.

It Might Get Loud has a slightly wonky premise: uniting these three guitar generations as they wax romantic about beloved first guitars, trot through key musical influences, and, most importantly, jam. In between reminiscing about their backgrounds growing up in Detroit (White), Dublin (The Edge), and the London suburbs (Page), the trio meet on a soundstage to warm their hands over the hearth fire of rock.

It Might Get Loud begins with an examination of some shared tendencies in the musicians. Though their approaches are different, Page, Edge, and White are united in their tendency not to leave well enough alone. All take to their guitars and amps like a 7-year-old girl to Barbie. They customize, tinker, and slice and dice to create their own unique sound, exemplified of course, by Jimmy Page’s double-neck “Stairway to Heaven” guitar solo.

But the way the trio innovate is utterly unique, reaching into the past and into the techie future in their quest for guitar excellence. White lives in the pastoral landscape of Franklin, Tenn., and is, despite being the youngest of the three, the most waist-deep in music history. Desperately in thrall to the old-timey, White sports a wood burned portrait of ’30s film star Claudette Colbert on his guitar and lives for the raspy sound of vintage bluesmen like Son House. “There’s a tension in that music you can feel,” he swoons, sounding very much like another blues groupie, R. Crumb in Terry Zwigoff’s outstanding documentary Crumb. Doubt his passion? Check out the blood smears on his guitar which Guggenheim helpfully zooms in on. White’s guitar sound strives for the raw gasps of those early, primitive blues recordings, and he admits to doing everything he can, including rocking a bargain basement Montgomery Ward plastic guitar to achieve the desired raw sound.

Representing the guitar future, The Edge is a yoga-practicing and Blackberry-toting gear head. Plugged into the mother of all amps, The Edge demonstrates how a simple chord can grow in power and beauty when the right pedal action happens. He’s obsessed with getting a distinctive sound with his guitars, and he’s using technology to perfect it. He also appears to have a humorless streak. Talking about the cock rock parody This Is Spinal Tap, he confesses, “I didn’t laugh. I wept.” It was all just too close to the truth for Edge.

And Page? What is there to say, except that at age 65 the man remains an unrepentant fan whose enthusiasm for the six-string is infectious. Page is the white-haired elder statesmen of the crew, the pioneer who perfected the chunky, “rude” sound of arena rock and never got the critical acclaim he expected for his efforts. Page turns out to have the most hypnotic presence as he traces his guitar-love back to an obscure, goofy British pre-rock fad, skiffle, through a succession of mildly geeky bands, and then The Yardbirds and finally heavy metal progenitor Led Zeppelin. The historical stroll down memory lane is fascinating, from Page’s epiphany that a life as a session musician wasn’t worth living to his description of recording Physical Graffiti in the acoustically soaring British mansion Headley Grange. White and The Edge can seem relatively joyless in comparison. Grinning like mad and strumming air guitar listening to a favorite Link Wray song “Rumble,” Page’s enthusiasm at the thrill of making music does much to carry an often plodding film along. When he plays old man second-fiddle to The Edge and White, some may chafe: in rock and roll, age is crueler than booze and drugs for taking rockers out of the running and diminishing their gifts next to the dumb luck of youth. Still, it’s hard to beat the giddy look both The Edge and White get as Page breaks into “Whole Lotta Love,” their professional reserve suddenly melting into a puddle of goofy fan adoration. If only there were more moments like that one.

And there you have it, essentially: three guys in three different countries hopelessly devoted to rock. But like onscreen lovers who lack a certain chemistry, the trio never seems to quite connect. Director Davis Guggenheim (An Inconvenient Truth) doesn’t help matters with the fractured, disjointed way he tells their stories. You get the sense Guggenheim kind of let his fan-enthusiasm take over, too dumbstruck at getting this trio of greats in one room to take control of his scattered, weirdly loosey-goosey film. Over time, the disjointed structure takes a toll. As the summit of strum builds toward the inevitable guitar showdown, it’s easy to feel a little let down as all that promised head-banging volume instead goes out more like a whimper.