It's a tough question. But Catherine Keener laughs at the tough questions. So here goes.

In her new film, "A Late Quartet," Keener, Christopher Walken, Philip Seymour Hoffman and Mark Ivanir portray members of a famous string quartet. They're shown in several scenes, rehearsing together or performing Beethoven in concert -- four nonmusician actors, sawing away at violins, a viola (the instrument of Keener's character) and cello.

An accomplished quartet -- the Brentano String Quartet -- does the playing we hear on the film's soundtrack. But what did the actors playing onstage actually sound like? Cats being tortured? Broken glass dragged across a blackboard?

Keener cackles. "Oh, you could recognize the pieces were supposed to be playing. We actually had to learn what we were being shown playing. We were given sheet music and we could follow along, playing along to a recording.

"But we weren't playing to speed, so to speak."

On a simple technical level, pretending to play an instrument on film is still a pretty tricky proposition. The old studio tricks of hiding the hands or substituting the hands of a great musician don't fool modern audiences. Keener's 13-year-old son plays the cello, and she knew from watching him that this wasn't going to be easy.


"We studied for a couple of months, all of us, before attempting it," says Keener, who has no musical background. "The hardest thing was just learning how to hold the bow. But when I cracked that code, it was a fantastic moment. That gives you the confidence, and with confidence you start to learn to play. You don't want to just be a dilettante about it, even if that's what you are. I wanted to be able to walk the walk a little bit."

That's what drew her to the film, the idea that she'd have a skill, a behavior that she'd actually "have to work at. You want to find things out that you don't know already, try something new. The preparation makes it appealing."

"A Late Quartet" is earning good reviews -- with Keener playing one-fourth of a quartet that is disintegrating. She is winning praise for serving as "the mournful passion" (Rex Reed, The New York Observer) of the piece. The "mournful" part comes from one particular scene, in which her violist discovers that her husband and quartet colleague (Hoffman) is cheating on her. Keener, famous for comedies ("The 40-Year-Old Virgin," "Being John Malkovich") and dramas ("The Soloist," "Please Give") doesn't have to say a word. We see her character deflate on camera.

"I remember feeling that way," the 53-year-old actress says. "That's what you call on for a scene like that. You remember how gutted you feel when you have that moment of realization, that somebody's cheating on you. You don't want to lay a trap for them, but you kind of do. You need to know. It's your biggest fear. It's a terrible position to be in, for both of you. You just have that 'What do I do now?' feeling. You find yourself having to figure out what the future holds, because that future just changed. And you're lost in the moment. You're lost."

But we're not crying for Keener today. She has movies by Paul Greengrass ("United 93"), her pal Nicole Holofcener ("Lovely & Amazing") and Charlie Kaufman (he wrote "Being John Malkovich") in the can. And even if she didn't master the viola for "A Late Quartet," she picked up life skills that she can apply every day.

"My son was practicing his cello last night when all of a sudden he was trilling," she enthuses. "And I went, 'Wow.' I was thrilled that he could do it, and thrilled that this movie taught me what that was!"