LOS ANGELES Three weeks before shooting began on "The Dark Knight," Heath Ledger called director Christopher Nolan to discuss an epiphany he had about his character, the Joker.
The key to the demented killer, Ledger said, was his voice. Without a menacing hiss, it would be a retread of Jack Nicholson's satirical turn when he played the character in 1989.
"He said he found the perfect one," Nolan recalls. "He had been studying ventriloquist dummies and thought they had terrifying voices. He was going to emulate one. I remember saying, 'Yeah, that sounds great.' When I hung up the phone I thought, 'God, I hope that's going to work.'"
There's little question now. The demonic voice floats through the myriad trailers promoting the film, opening Thursday night in many cities. And the late actor's performance eight months from the Academy Awards is garnering Oscar talk.
"He wouldn't even really rehearse with the voice," says Christian Bale, who plays Batman. "He held it back a little, waiting for the cameras to roll. But when they did, we knew he was on to something special."
Great villain voices usually are, says film author and historian Leonard Maltin.
"It can be the most memorable element of the character," Maltin says. "You think about the great ones: Anthony Hopkins' Hannibal Lecter or the great Peter Lorre or the granddaddy of them all, Darth Vader. In a way, those characters are defined by that voice."
But what makes for an effective one? It's more than theatrics, more than a growl or a snarl.
Some directors prefer bad guys who cackle. Others like villains whose pitch never changes, even when they do terrible things.
"It's tough to define, but you know it when you've found it," says Sam Raimi, director of the "Spider-Man" franchise, who has cast Willem Dafoe, Alfred Molina and Thomas Haden Church in evil parts.
"Personally, I love a villain who has a good laugh," Raimi says. "My favorites are Margaret Hamilton in 'The Wizard of Oz' and the Nazi in 'Raiders of the Lost Ark.' Those people who can laugh when they're committing atrocious acts are truly horrifying."
Heavies without good voices, says Steve Mason, a columnist with Hollywood.com, are a little like guns without bullets: frightening on the surface but harmless when it's time for action.
Think Arnold Schwarzenegger's Mr. Freeze in "Batman & Robin," whose clunky delivery left audiences chuckling rather than chilled. Or John Travolta's Terl in "Battlefield Earth," whose high-pitched baddie helped doom the film to IMDB.com's basement of the worst 100 movies of all time.
Mason says some of the most effective villain voices in Hollywood lore feature flat accents that vary little in pitch: Hal in "2001: A Space Odyssey"; Hopkins in "The Silence of the Lambs"; Glenn Close in "Fatal Attraction."
"Daniel Day-Lewis and Javier Bardem won Oscars with voices that were hard to place," Mason says. "It can give your characters a sense of isolation."
Bardem, who won his best-supporting-actor Oscar for villain Anton Chigurh in "No Country for Old Men," says he was just trying to pronounce his words correctly.
"I have such a thick Spanish accent, I didn't want to give away I was not from here," he says. "They (directors Joel and Ethan Coen) loved that. They said it would throw people off if you couldn't tell where he was from."
To Day-Lewis, who claimed the Oscar for best actor as a ruthless oil baron in "There Will Be Blood," the sound of his Daniel Plainview was critical.
"I must have gone over hours of Dust Bowl recordings," he says. "The accents and tone can be one of the hardest things to get right, but if you don't, you'll lose your audience."
Bob Corff, author of "Achieving the Standard American Accent" and voice coach to actors including Bardem, Faye Dunaway and Forest Whitaker, says the key to a menacing tone can be just slowing down.
"Whether you're looking for a drunk or villain accent, it's very effective to speak your words carefully," Corff says. "In either case, you're trying to hide your true nature. And that's chilling. You don't need to be theatrical if you're saying "I'm going to cut your head off.' That's scary enough."
The patriarch of modern cinema villainy, James Earl Jones, calls Day-Lewis' threatening monologue in "Blood" "the scariest thing I've heard in years. The scene where he says, 'One night, I'm going to come to your home and cut your throat.' It was so cold, so disaffected."
Jones says it wasn't until his second film playing Vader that he learned what it takes for a voice to make spines tingle.
"At first, I was trying to put heart in character, and (director George Lucas) said that was the problem," Jones says of Vader in 1977's "Star Wars." "He wanted something that could witness and cause all this destruction and not be moved by it."
By 1980 with "The Empire Strikes Back," he understood what Lucas meant. In preparing Jones' lines, "Empire" director Irvin Kershner read the part into a tape recorder to give Jones a sense of the cadence and rhythm of the voice.
"I thought he did a better Darth Vader voice than I did," Jones says. "It was a little raspy and completely cold. It seems to be what Heath has done for 'Batman,"' Jones says.
Certainly, Ledger's fatal prescription-drug overdose in January also has lent a haunting nuance to a role that has become his swan song. Whether audiences can separate actor from character will decide the destiny of the film and the lasting memory of the star.
But Nolan says the Joker's on-screen creepiness comes from Ledger's skills, not his fate.
Ledger had one goal in creating the Joker's voice: un- predictability, Nolan says. Ledger moves his voice a full octave up or down in the role peppering it with a maniacal laugh a vocal performance that even crew members were talking about.
Voices, particularly in a genre such as comic-book movies, can be freeing for an actor, Bale says. "You can feel pretty silly in a rubber suit," Bale says. "But if you allow yourself to fully get into character, to embody what you're playing, it helps on screen."
And few are questioning that it helped Ledger. A few months ago, director Ang Lee heard Ledger hissing the line "Let's put a smile on that face" as Lee walked through the ShoWest convention of theater owners.
Lee, who directed Ledger in "Brokeback Mountain," initially did not recognize the voice until he looked at the screen.
"I couldn't believe that was Heath," Lee says. "He was such a different person, used such a different voice for 'Brokeback Mountain.' It's haunting, how much he disappeared into his characters. It wasn't until I heard that, that I realized just how gifted he was with his voice."