They meet every day. His house or hers, mostly hers.

Sometimes they just sit there, drained of ideas, despairing. Sometimes there are disagreements, smouldering silences. Sometimes the electricity crackles between them as they bat lines back and forth, images, situations, gags, gleefully interrupting, eyes snapping, hands punctuating the air.

Betty Comden and Adolph Green, who open Sunday for two weeks at the Kennedy Center's Terrace Theater, have been meeting like this for 40 years. They are married to other people with careers of their own. They each have children, a house, a separate life.

But out of those daily meetings has come a comedy collaboration that has changed the face of Broadway, and maybe Hollywood too.

How about "On the Town," a landmark musical of 1944 that launched not only Comden and Green as authors -- and actors -- but also Leonard Bernstein as pop composer?

How about the Gene Kelly movie "Singin' in the Rain," voted one of the 10 best films of all time? How about Fred Astaire's "The Band Wagon," "Auntie Mame," "Bells Are Ringing," to pick the more memorable screenplays, and these Broadway block-busters: "Billion Dollar Baby," "Wonderful Town," "Say Darling," "Subways Are for Sleeping" and that Art Deco doubletake, "On the 20th Century"?

It started with a nightclub owner in 1939. The guy didn't have a liquor license. Didn't even have a phone, according to legend. His name was Max Gordon (not THE Max Gordon, everyone except him always adds), and he decided he could use a little cabaret act for his place, the Village Vanguard.

So he talked to this kid who hung around there a lot and she said why not try her? She and some friends had been working up an act....

Her name was Judy Tuvim, but since Tuvim means holiday in Yiddish, she had changed it to Judy Holliday.

They called themselves the Revuers, and they couldn't afford a writer so they wrote their own stuff. John Frank composed the music, mostly to tunes that Adolph Green would hum at him. Green and Betty Comden had met while she was at New York University, and he had run into Judy at a summer camp.

"It wasn't exactly a hit right away," Max Gordon said the other day (he still runs the Village Vanguard, and now he is THE Max Gordon because the other one died), "but they gradually built an audience. They created their own crowd."

The crowd was definitely the right one to attract in the 1940s. It included many of the New Yorker stars -- Perelman, Benchley, Ogden Nash -- who were Comden and Green's heroes. Even today in their latest musical, "On the 20th Century," there is a reference to the Algonquin Round Table.

And then came "On the Town."

It wasn't simply that the show made them. "On the Town" was a seminal event to rank almost with Gershwin's "Rhapsody in Blue" -- in reverse, so to speak, because instead of introducing a songsmith to the Philharmonic it brought the talent of what people love to call a classical composer into the pop world.

Drawn from a Jerome Robbins-Bernstein ballet, "Fancy Free," the musical had an offhand quality, an immediacy and freshness that lifted the hairpieces of sleepy Broadway audiences unaccustomed to the skill of serious artists. Agnes DeMille's choreography, also solidly rooted in formal ballet, popped their eyes. And the Comden-Green book and lyrics had exactly the right touch: brittle, slangy, quick and shiny -- very New York.

With mouthy Nancy Walker as a cabbie, the delicate but leggy Sono Osato as the dancing star, Comden as anthropologist and Green a leave-happy sailor, "On the Town" opened a new horizon to the Broadway musical.

Just as the typical Comden-Green song lyric is wedded to the plot (making it perhaps less apt to become a hit on its own in the sheet-music trade), so their plots stick close to the homely realities of life.

"On the Town" was about three sailors on leave in the city trying to find Miss Turnstiles, the subway equivalent of Miss Rheingold. "Bells Are Ringing" was about an answering service. "Bandwagon" grew out of an MGM contract to do a film for Fred Astaire, who was then 54 years old and semiretired, as Variety would say.

"We had all these elements," Green said, "Astaire and Oscar Levant, an old friend of ours, and songs by Schwartz and Dietz which weren't exactly the latest thing (the original had descended upon Broadway in 1931), and we couldn't figure how to put all these things together. So we faced the facts and wrote about an aging star. We put as much of ourselves into it as we could."

(Not to imply that they themselves were aging stars at the time. Who's Who has Green born in 1915 and Comden in 1919, but a book on musicals insists they are the same age and went to NYU together. Take your pick. In any case, today they both look vigorous, organized and barely out of their 40s.)

In an early scene the dispirited Astaire arrives in Grand Central Station to be greeted by his young friend with cowbells and a big sign. This actually happened to Green once: Comden met him carrying a huge sign that said, "Adolph Green Fan Club."

It's that kind of friendship.

They seem to write about the entertainment world more than any other, and one of their most durable and delicious conceits is the one about the top-heavy dramatic turkey that collapses of its own pompous weight.

In "Bandwagon," Astaire is saddled with a perfectly dreadful musical based on Faust. The show fails, of course, which leads to a wonderful payoff scene where the cast turns a dismal post-mortem party into a whole new musical. It's an affectionate sendup of that classic bit: "I know how we can save the college! We'll put on a show!" Everyone from Jack Oakie to Donald O'Connor did that number.

"On the 20th Century" opens with a horrendous scene from an imaginary something called "The French Girl," a mythical flop about Joan of Arc, and later it toys with an even more hilariously bad idea, "The Passion of Mary Magdalene."

Such overstuffed vehicles inspire Comden and Green to veritable conniptions of brilliance.

There's a song about "Veronique -- she closed her door/And started the Franco-Prussian War" and some nonsense about Prometheus and Promethea and an entire wild production number from a gigantic unwritten musical.

(I have to tell you: The reason why they changed the name of the original "20th Century" to "On the 20th Century" is that one of the backers was into numerology and demanded five more letters in the title.)

George Gershwin used to say, "I've got so many songs in my head, if I lived a thousand years I couldn't write them all down." You get that feeling about Comden and Green. Who knows how many musicals died aborning in those daily conferences?

One for certain was "Say It With Music," planned as a great film tribute to Irving Berlin in 1965, with his songs spanning half a century, Julie Andrews, Vincente Minnelli directing and Arthur Freed producing.

"Berlin was crazy about the script," said Green. "He jumped on the phone and told us so, and we thought that was all we needed. He was so excited we thought we'd surely get it done."

The plot, which they have never talked about before in public, was a kind of musical "Intolerance," with three parallel stories, turn of the century, 1920s, 1960s, intercutting and ending on the same note.

"But it was just too much money," Comden said. "They absolutely had to have Julie Andrews, and that was expensive. We mentioned a girl named Barbra Streisand but they said no, she wasn't big enough. Too unknown."

A couple of years ago they started work on a movie biography of Busby Berkeley, but that died too. They didn't want to talk about it.

"It takes a lot of floors you can get up off of," Green said. He laughed.

Their working technique hasn't changed over the years. They meet usually in the booklined study of the quietly luxurious four-story townhouse on the Upper East Side where she and her husband, designer Steven Kyle, live.

Composer Cy Coleman tells how he worked with them for "On the 20th Century": "It was wonderful. We'd rush around from my house to his house to her house, and we had these cassette machines. There'd be a lot of staring. We'd sit around and talk. And then something would catch fire and I'd go to the piano, and the cassettes would come out. We all know how to do musicals, we know our trade, it's not a question of that. It's a question of what it'll be."

She: "We rarely do homework separately. Everything is together. We don't divide the work up. We develop a mental radar, bounce lines off each other."

He: "Sometimes it's a study in despair and inactivity. We don't have big fights. If a flareup starts, we make sure to stamp on the flames."

She: "But there aren't too many differences between us on the artistic level."

He: "Writing is a source of joy for us. Acting too. We started as performers, after all."

She: "We love that primitive feeling of being in front of an audience. You see yourself in a different way."

He: "We like the new comics. You hear some complaints about bad taste and how there's no wit anymore, but I disagree. Bad taste is a product of intelligence."

They rarely interrupt each other. They hardly even have to exchange glances to see who's going to answer the question.

The spouses accept this remarkable friendship. Kyle, Comden's husband since 1942, owns a store called Americraft, and has been for years an audience of one at their brainstorming sessions.

When they couldn't decide which of several endings to use for "Singin' in the Rain," it was Kyle who suggested they use them all.

It worked.

Green has been married since 1960 to Phyllis Newman, an actress, singer and TV personality whom he met when she understudied Judy Holliday in "Bells Are Ringing," which also was made into a movie.

They have worked in Hollywood, don't like it all that much. Before "On the Town" they wrote two numbers for a Don Ameche musical but both were cut. And in '63 they gave movieland the velvet needle with "Fade-out, Fade-in" starring Carol Burnett. One mordant line was all they needed to destroy all the witless showbiz gossip columnists who ever gushed. It has her burbling about "... far-off Vienna, that beautiful country which gave us Maurice Chevalier...."

Last season the writers returned to the stage in a new edition of "A Party With Betty Comden and Adolph Green," a happy show that charmed its first audiences in 1958. They still run it out now and then. They do a lot of benefits.

But that revue celebrates the past, sketches and songs from their works. The daily meetings are about the future.

He: "We're planning a new show with Cy Coleman."

She: "He did the music for 'On the 20th Century,' you know."

He: "And also we have a movie idea...."

She looks at him. He looks at her. You wonder if something has just snapped into place and if you are part of it.

Let's see, there's this newspaperman, and he comes to interview these famous writers, and....