THERE ARE people in Washington who regularly lock themselves into small, dark, padded rooms and go bananas.

They pretend to be hillbillies, gangsters, Nordic kings, clerks and pizza chefs. Some of them impersonate furniture. One of them almost always wears a loud hat.

They are making radio commercials. And the fellow with the hat is Marvin Himmelfarb.

Himmelfarb writes and produces some 500 radio commercials a year for the local ad market -- an industry that generates about $45 million in annual business. And he is one of the most innovative influences on an industry in which creativity often takes a back seat to Lord High Demography.

His considerable charm rooted deeply in bluster, Himmelfarb, 42, talks fast and often funny; he dresses eclectically, and he laughs easily. His laugh begins suddenly, somewhere beneath his reddish-brown beard and mustache and neon-white Irish walking hat, and pogos across the room like a crazed rabbit in search of high-ranking Democrats. But then, Himmelfarb's sense of humor is legendary: "Hello, Sam's Submarines, Tacos, Pizzeria and Won Ton Carry Out. We deliver anywhere, you name it we'll make it, anytime, day or night, Sam is right."

"Yes, I'd like one Sam's Special please."

"One Sam's Super Sub with ham, sausage, chocolate fudge, provolone, cheese, anchovies, egg foo yong, artichoke, Russian dressing, chile dip and hot peppers. . ."

"I thing I'll skip the hot peppers."

"Kill the hot peppers! Okay, where do you want it sent?"

"Quince Orchard Apartments in Gaithersburg."

"No kidding, Quince Orchard -- you live there? I heard some great things about that place. . ." "There are 75 to 100 voice talents and six or seven studios doing quite well in just radio commercials here," says one of Himmelfarb's competitors. "From the standpoint of what's healthy and dynamic for the Washington radio market, Marvin has had a very definite positive, catalytic influence on the industry. But his stuff just isn't scientific."

"It's silly and annoying," says another. "All those dialogues and trialogues . . . "

"I prefer of course to call them . . . uh, humorous," says Himmelfarb with a anxious giggle.

He writes and produces his radio and television spots for the Abramson-Himmelfarb advertising agency, of which he's a partner. The agency's biggest radio clients include:

The American Service Center (The commercials have starred Vincent Price -- whose giddy reaction to the "Realize your driving ambition" slogan won Himmelfarb a Clio nomination -- Jose Ferrer, local actor Tim Rice playing a ventriloquist who sports an entire singing chorus of dummies, and most recently, Max and His Singing Cats);

Arena Stage (Himmelfarb says last year's spot for "Duck Hunting," with its several poignant soliloquies by Arena's Stanley Anderson, is probably his favorite commercial.);

Woodward & Lothrop; WJLA-TV (Channel 7); Ourisman Dodge; Marion Barry's mayoral campaign, and the ubiquitous real estate management firm of Dreyfuss Brothers -- all those ads for places like Quince Orchard and Peppertree Farms, including the two-year Wiltons" hillbillies-in-search-of-an-apartment series.

"A commercial is like a joke," Himmelfarb says. "Somebody'll tell it once, and the punch line will be funny. And then they'll tell it again, and about the third time they'll tell it again, and you'll say 'I've heard it.'

"Unless," he says, punctuating the words by nodding his head, " unless you enjoy the storyteller . Then you can listen to the joke over and over again -- because what you like is the way it's told.

"The No 1 thing, no matter what, is does the spot sell? No. 2: If they sell -- and they're still a little bit annoying and silly -- so be it."

Himmelfarb has an ear for talent. He goes to local theater almost religiously, and has found several of his fairly regular "stable" of voices -- some 30 to 40 actors and announcers -- as a direct result. (He also found his wife, Lisa Rafel, when she came to audition for one of his commercials.)

He will listen to anyone once (many of them, he says only once), tries to use as much local talent as he can, and would some day like the time to write a play or two -- as he did for Davey Marlin-Jones' now-defunct Washington Theatre Club, where Himmelfarb found himself about 15 years ago able to spend many of his non-advertising agency hours at rehearsals and readings, and where he says he learned truckloads about theater (and thus commercials).

"I'd leave work early, and from 2 in the afternoon 'til 2 in the morning I'd be there, at Davey's knee. And that's where I learned a lot of what I know and use of theater -- the pacing, the rhythm, the spine of a piece."

Himmelfarb is a true native Washingtonian (an alumnus of both Coolidge High School and American University). He was given his first advertising job just after college by Doug Bailey, an advertising man who then taught at American University. "He said he liked my chutzpah," says Himmelfarb.

The next few years Himmelfarb spent writing advertising flyers, spots and inventing promotions for shopping centers -- a relatively new thing in 1960. Amony his early exploits: hiding silver dollars in 10 out of 1,000 cherry pies he then sold in the Congressional Plaza parking lot; dressing up as a clown; importing "man-eating piranhas"; and introducing cartoons on Channel 5 in a Deputy Dawg costume for Top's Drive-In, the cartoon's local sponsor. Himmelfarb learned radio while working for Bailey -- where he also worked for a while with Walt Kramer, who is now the producer (and voice of the Morton character) of the ubiquitous Fotomat radio spots.

He struck out on his own for a couple of years ("a disaster -- I had no idea how to do business") until he found David Abramson and formed a partnership in 1965. The team's big break came when they convinced Dreyfuss Brothers that real estate could be sold not just in the Saturday real estate section but also on the radio -- and also a little differently than most.

Himmelfarb mimics the phone call: "Marvin, really -- 17 voices and a chorus? For a 60-second spot?"

Himmelfarb prefers not to write in the office, but rather in the midst of as much noise and activity as possible. Restaurants are good; he says he picks up a lot of ideas from nearby conversation. When the copy is written, the action moves to a nondescript red-brick building in Falls Church. There, in a dark, carpeted recording room, Himmelfarb and company convene at least once a week with the dozen or so actors, actresses and announcers he has hired for the day.

In an atmosphere not unlike a casual dinner party for friends, the voice talents trade stories as they wait in the lobby for Himmelfarb to call them into the studio. Once inside, Himmelfarb will have them do a run-through "for time." If it's too long -- and it often is -- he'll either have them speed up the delivery or begin cutting the copy. He does it in a matter of minutes, communicating the changes to the headphoned announcers through an intercom and a soundproof window.

He uses more than one voice whenever he can, and his announcers have the Theater Club to thank for that. When he uses just one relatively straight-voiced announcer, which he does a lot, "I still look at it as a soliloquy -- it begins, builds and ends."

"He can pull together a real mood -- even in a retail spot," says Howard Ross, a New York actor whom Himmelfarb has used most often as "the voice of Woodies" for the past three years. "He's fast. He knows what's necessary to make a spot do a job, and he can cut out the garbage in a moment."

"Marvin will have you do 17 takes, or 72, but if the first one is right, he'll have the confidence to say 'That's it,'" says Naomi Robin, a New York actress Himmelfarb has been importing to his weekly recording sessions ever since he "discovered" her in a visiting cast of "Godspell" last year.

"Sure, he's eccentric," says another voice of perfect diction. "But that's part of the Marvin mystique."

That mystique is one reason that the walls of Abrians on-Himmelfarb's "sound room" at their downtown offices are dotted with Addys -- the local advertising awards.

Down the hall in his office, Himmelfarb stands behind a desk that groans audibly under several mountains of paper, audio and video tape reels and cassettes. "You know how some people with offices like this say they can still find anything they need in a second?" he asks, gesturing around. "Well it's not true. I can't find a damn thing in here."

There is plenty of work, even though -- relative to its size -- Washington is not a big advertising city because it has very little industry. Andrew Ockershausen, executive vice president of WMAL-WRQX radio and a Washington advertising watcher for some 30 years, calls the city's 100 or so advertising agencies "mostly white-collar agencies -- government is this town's biggest industry, but then that means a lot of people interested in cars, homes, apartments, clothes, stereos."

The industry recorded its biggest growth in the late '60s and early '70s and has since leveled off, says Himmelfarb, and competition is keen.

"The one great thing about doing local retail work is that you can do the greatest, funniest, most marvelous real estate spot on Wednesday -- but if nobody shows up looking for apartments on Saturday, you better believe you'll get a phone call Monday morning that says, "Uh, Marvin . . . '"