"Bright. Crisp. Clean. Pure," says the silky smooth, perfectly masculine voice on the beer commercial. "This is Budweiser. This is beer."

Quick, who is that? Hint: It's a big movie star. Though his name is never mentioned, the makers of Budweiser are banking that you'll get it eventually — and that you'll say "Wow!" when you do.

Twenty years ago, voiceovers were the domain of the baritone radio announcer or the character actor. No longer. These days, more A-list stars than you might imagine are cashing in.

Kevin Spacey's pitching Honda. Kelsey Grammer does Disney. Kiefer Sutherland voices Apple commercials, and his dad, Donald, did Volvo. There's Sean Connery (Level 3 Communications), Christian Slater (Panasonic), Gene Hackman (Oppenheimer Funds) — oh, and then there's Julia Roberts.

That's right, Julia Roberts, in a recent campaign for America Online.

It seems no one's too rich or famous to do a voiceover. It's not too hard to see why the celebs like it: It's an easy, lucrative form of work — a few recording sessions where you can show up with messy hair and no makeup. The more difficult question is why advertisers are willing to spend a huge chunk of their budget on a star whose voice, however distinctive, likely won't be recognized by many.

"Honestly, sometimes I'm mystified," says Maureen Kelly, a casting director who has worked in the voiceover field for two decades. "I guarantee you, most people couldn't tell the AOL voice was Julia Roberts. I'm just not sure why advertisers spend this astronomical amount of money when the voice isn't even identifiable."

By astronomical, we're talking seven figures, easily. Although companies won't say how much they pay, industry experts say a megastar like Roberts would have to make well into that range.

Or George Clooney, that mysterious Budweiser voice. When Anheuser-Busch was searching for "a classic voice" last year, the company hit on Clooney as the perfect embodiment of its product. "George Clooney — it's almost a brand in itself," says Dan McHugh, vice president for trademark brands. "It just made a lot of sense for us."

The idea, says McHugh, is that the consumer will "sort of know the voice. They may not necessarily place it right away, but when they do, they say, 'Wow!' It's that whole intrigue of discovery." In other words, the "cool" factor is higher because there's mystery involved.

Laura Cheshire, a commercial director in New York, says many celebrities have distinct vocal patterns that set them apart — recognized or not.

"They have a special authority, even if you can't name them on the spot," says Cheshire, who directed a current Panasonic ad with Christian Slater (he participated by remote hookup.) "It's usually worth the expense, because you get more emotion — which sells more product."

Advertisers didn't always have such an array of choices. Twenty years ago, says Linda Weaver of the Access Talent agency, jobs went primarily to announcers from the radio world, with the so-called "Voice of God."

Martin Sheen was one of the first well-known actors to make the plunge, voicing ads for Pepsi and Maxwell House in the 1980s.

Eventually, voiceovers became seen as acting jobs, not announcing jobs. "I can't tell you how often I am told, 'not announcer-y, not announcer-y,' " says Kelly, who owns the Just Voices casting house. "I hear it from everyone."

In recent years, many rank-and-file actors have turned to voiceovers for a steady stream of income. The best of them have an impressive repertoire: they can do sexy, perky, the harried mom or the guy who drives fast cars. One good national commercial can bring in $15,000 to $20,000. A successful voiceover career can yield a comfortable six-figure income.

"I tell my theater actors, do this, and then you don't have to go to Little Rock to do that third production of 'Fiddler,' " Weaver says.

American stars still often head overseas for commercials that won't be seen at home, but lately, doing it at home seems OK, too. Catherine Zeta-Jones appears on camera for T-Mobile. Ellen DeGeneres does American Express. The most respected actresses become the "faces" of fashion and beauty houses — Nicole Kidman (Chanel), Gwyneth Paltrow (Estee Lauder), Hilary Swank (Guerlain), Charlize Theron (Dior). Brad Pitt even did a Heineken ad last year.

Also, this is a time when big stars by the droves are voicing animated films — Robin Williams, Antonio Banderas, Cameron Diaz, Ben Stiller, and on and on.

As for Clooney, among the hottest male stars on the planet, he preferred to do a voiceover rather than appear on camera, says McHugh of Anheuser-Busch. Clooney was conscious of the talk of stars selling out, and "he really liked the idea of a voiceover," McHugh said. "This felt a lot more genuine to him."

There is talk in the voiceover business of "name" actors pushing aside what Alison Fraser, a New York theater actress, calls "the bread-and-butter" people.

Twice nominated for a Tony award, Fraser nonetheless made her living for 12 years primarily on voiceovers. She says she understands the appeal, for an advertiser, of a Clooney or a Roberts, and respects the choices of both actors and advertisers.

Still, she says, she can't help but feel a pang when she hears of a huge star doing a voiceover campaign. "I think 'Oh, geez,' " Fraser said. "Why do THEY need to do that?"