* "Birdman" is strong outing for Keaton, opener for Venice
* Change of pace for Mexican director Inarritu
* Mostly set in Broadway theatre, production resembles play (Updates with director, Keaton comments)
By Michael Roddy
VENICE, Aug 27 (Reuters) - Former "Batman" star Michael Keaton gave a soaring start to the 71st Venice Film Festival on Wednesday as a crestfallen superhero in "Birdman", a film its Mexican director Alexandro Inarritu called an experiment that could have failed miserably.
The film brings starpower that Venice, the world's oldest film festival, needs to keep itself from being sidelined by the celebrity magnet of Cannes in May and industry powerfest the Toronto Film Festival, which opens next week.
Noted for his arthouse movies "Babel" and "21 Grams", Inarritu switches gears in this Fox Searchlight production, also starring Emma Stone as Keaton's daughter, who is just out of drug rehab, Naomi Watts as an actress desperate to make it on Broadway and Edward Norton as the foil to Keaton's character, Riggan Thomson.
"Michael was a pioneer of those superhero roles and having some time and perspective I thought his knowledge about it, his experience about it, will get something very powerful for this film," Inarritu said at a post-screening press conference.
"Michael was crucial to make this film, without him I think this film couldn't be made."
"Birdman", Inarritu's fifth feature film, is set mostly at a Broadway theatre where the Keaton character hopes to make a comeback in his own theatrical adaptation of a short story by the late American writer Raymond Carver, "What We Talk About When We Talk About Love".
Inarritu, who filmed the movie in a faux single-take style so it looks like the camera never stops, said "Birdman" had been an experimental project.
To make this point to the cast, he even sent them photographs of the French high-wire artist Philippe Petit making his famous unauthorised tightrope walk between the twin towers of New York's World Trade Center in 1974.
"That was the image and the ambition of this film, or at least the execution of this film was very much like this," he said. "We were kind of crossing without a net with the possibility to fail absolutely and miserably and be laughable."
The film shows touches of Latin American magical realism, spectacular car crashes and a colossal, computer-generated monster - but the effects are pretty much an afterthought to the imposing, theatre-like production.
Keaton, asked if his Batman successes had undermined his career, said his past superhero role was like "the giant elephant in the room". But he joked that he'd recently returned from Africa and that "I love elephants so I'm okay with the elephant in the room".
The plot of "Birdman" deals with a question haunting Riggan, who gave up being the superhero Birdman, much like Keaton gave up doing Batman in 1992. Riggan asks himself: Do I still exist?
"I wasn't present in my own life," the character says as he wrestles with having missed his daughter's birth, blaming himself for her drug addiction and for the break-up of his marriage to his wife, played by Amy Ryan.
He has sunk far from the heady heights of his "Birdman" alter ego but is inexorably drawn back to the role.
Inarritu plays with the age-old love-hate relationship between Broadway and Hollywood, which is brought into the open when a venomous New York Times critic, played by Lindsay Duncan, tells Riggan her review will kill his play.
In the lead up to opening night, Keaton and Norton play out an intense, almost Shakespearean drama, with the critic trying to show up Keaton's Riggan character as a Hollywood has-been with no place on Broadway.
Stripped to the two-hander of Keaton-Norton, the scene is a gripping tour de force and results in Keaton trashing his dressing room after Norton has seemingly crushed his ego completely.
Trade publication Variety has called the film "a triumph on every creative level, from casting to execution, that will electrify the industry, captivate arthouse and megaplex crowds alike, send awards pundits into orbit and give fresh wings to Keaton's career".
(Michael Roddy is an arts and entertainment correspondent for Reuters. The views expressed are his own) (Writing by Michael Roddy; Editing by Raissa Kasolowsky)