You might think Jimmy Page doesn't need to do air guitar since the Led Zeppelin axeman can obviously play a real one, but a new film shows that rock legends -- some of them anyway -- can't help it.

Page gives this away while strumming along on an imaginary guitar to a vinyl recording of "Rumble" by Link Ray -- the little known but influential 1950s leather-clad guitarist who has been called the "godfather of the power chord."

The episode is part of a documentary premiered in Europe on Tuesday night at the Berlin Film Festival, a tribute to the iconic instrument that teenagers down the ages have dreamed of mastering.

The film, made by the director of Al Gore's 2006 Oscar-winning "An Inconvenient Truth", has a title that doubles as a warning: "It might get loud."

This is not superfluous, as Davis Guggenheim brings together an Englishman, the Irishman and the American who have made their careers making a whole lotta noise, letting them jam and talk while the camera rolls.

Page is from the 1960s and 1970s rock band Led Zeppelin, The Edge is part of U2 and Jack White is one half of drums-and-guitar duo The White Stripes and also fronts The Raconteurs.

"We checked but Jimi Hendrix wasn't available," Guggenheim joked.

The three also give revealing private interviews: Page in the English manor house where "Stairway to Heaven" was recorded, Edge at the school where U2 formed and White frightening cows in rural America with a rudimentary home-made electric guitar.

This is interspersed with archive footage, some of it never seen before, including a clip of Page the schoolboy saying his ambition was to work in "biological research".

This drew a laugh at the Berlin premiere as his later drug use in Led Zeppelin suggested his real calling was more in chemistry.

Edge, wearing a hat throughout, is modest and quiet, Page is happy and highly enthusiastic -- never more so than when digging Link Ray or showing us round the manor house -- and White is funny but appears slightly ill at ease.

There was also a certain "tension," Edge told reporters in Berlin, since all three -- Page is 65, Edge is 47, White is 33 -- come from three very different generations of music.

"There's going to be a fight," White says at the start of the film.

"Each generation feels a need to push aside the previous generation ... We each represented thee eras of rock and roll that were to some degree in opposition to each other," says Edge.

U2, for example, were formed in the mid-1970s and inspired by the punk movement, which was dedicated to sweeping away the kind of self-indulgent practices of rock bands of the time famously satirized in "This is Spinal Tap" -- for example Led Zeppelin.

"There are a few things that I still hold on to from my punk early days, the ethos. Air guitar is definitely out," Edge says.

The Berlinale runs to February 15.