Ray ''Uh-Huh'' Charles' grin has become synonymous with diet Pepsi. Same with Candice Bergen's smirk and Sprint. But other celebrities prefer to be heard and not seen in TV commercials. That rasp informing us that ''Spray 'n Wash gets out what America gets into'' belongs to Lauren Bacall, and the eerily timbred voice selling Volvos is Donald Sutherland's. More and more stars are looking for such uncredited voice-over work. ''A mysterious kind of cachet has developed around it,'' says Chas Cowing, voice- over director of the J. Michael Bloom and Associates talent agency in New York. ''On-camera participation downgrades the viability of an artist. That doesn't happen with voice-overs.'' It's also easy work. ''You don't have to wear makeup and they don't care if your hair is frosted,'' says Broadway star Alison Fraser (The Secret Garden), who does about 100 voice-overs a year. And it can be easy money. One campaign of four commercials could pay a celebrity $250,000, industry insiders say. Why do companies hire celebs who are not identified? ''There's a visceral response to a voice that is familiar,'' Cowing says. ''When we hear Gene Hackman, we might not recognize him, but we know the voice. Also, the CEO of a company wants to be able to go to a cocktail party and say, 'Guess who I just spent the day with?'''

DON AMECHE CLUB MED FAME: The Story of Alexander Graham Belt; Cocoon SETTING/CONTENT: Bright series in which sun worshippers young and old frolic on the beach. PITCH: ''Forget all the things you can do on a Club Med vacation, and we'll show you how even doing nothing can be something unforgettable.'' VOICE APPEAL: ''We needed a toughness and a warmth at the same time. It became a single-minded pursuit of Don Ameche.''-Alan Blum, vice president, senior copywriter, TBWA

LAUREN BACALL SPRAY 'N WASH FAME: Bogie's widow; Robards' ex; whistler SETTING/CONTENT: Norman Rockwell meets thirtysomething: Casually stylish mom smiles indulgently as children make mud pies and put watermelons on their heads. PITCH: ''In a world no bigger than a sandbox, no deeper than the mud between toes, it's Spray 'n Wash that has gotten out...'' VOICE APPEAL: ''We'd say, 'Can you make that sound more smiley?' and she'd say, 'Smiley?'''-Joe Holman, senior advertising manager, DowBrands

DONALD SUTHERLAND VOLVO FAME: Came thisclose to being Julia Roberts' dad-in-law; Ordinary People SETTING/CONTENT: Film noir dramatization of angelic physical therapist working with accident victims, to the sounds of an angelic choir. PITCH: ''She instilled her horror of accidents in her husband, who happened to run a car company called Volvo'' VOICE APPEAL: ''His voice sounds scholarly and professional. We did not want (the ad) to sound learned.''-Robert C. Austin, director of communications, Volvo Cars of North America

MICHAEL DOUGLAS INFINITI FAME: Shining Through; Wall Street; Fatal Attraction SETTING/CONTENT: Three spots in which accountant types reclaim their youth and toss aside the car phone while hugging the curves in their leather-lined sedans. PITCH: ''It's a car that has the Germans shaking in their lederhosen.'' VOICE APPEAL: ''Confidence, a bit of irreverence, a level of classiness, elegance, respect- he kind of personifies all of those.''-Robert M. Paske, general marketing manager, Infiniti