In the city of politics and government, power and influence, ego and id -- Washington, that is -- no one likes to play second fiddle.

Unless, of course, the issue at hand is a string quartet.

"I actually prefer the second violin part," says ex-Supreme Court Justice Abe Fortas. "If there were third violin, I'd even play that . . . I enjoy the inner voices."

He counts himself among the hundreds, perhaps thousands, of local souls who have taken refuge of an evening in playing chamber music. Washington in winter is alive with the strains of chamber music, so called because it's better suited to a cozy room than a concert hall. Fans can sample such morsels as duets, trios, quartets and quintets by composers old and new at all hours in public places. But Washington behind closed doors offers music-making of a different sort, for the people who would rather play than listen.

Now if that conjures up stuffy salons peopled by fops in powdered wigs, conjure again. Instead, imagine friends gathered in someone's living room, mayber in front of a crackling fire, to share an enthusiasm and sip a little wine. Banish thoughts of snobbery about in a circle, this could be poker and whiskey, home-movies and beer, though sometimes the spirit's more intense.

"Let's face it," says Jeffrey Binckes, a satellite systems engineer who plays piano, "how much can you express yourself in a third-order differential equation or a mass/power budget for a satellite? It's my profession, but there's no way I can put my uniqueness in that. On the other hand, I can play a Brahms piano trio somehow a little bit different from anyone else."

A recent evening at the Cleveland Park home of Joe Burstein, a public housing lawyer about town, combined many of the elements that can make chamber playing a pastime without equal. To wit: cooperation instead of competition, scant backbiting, sustained concentration, some real artistry and, rare among social activities, the getting together of far-flung generations simply for the fun of it, no strings attached. There was, in this instance, a four-decade gap between the youngest and oldest player, and it mattered not a whit.

A petite man with a white mane, the 65-year-old Burstein, in freshly pressed slacks and topsiders, hovered over an end table before the other players arrived. He busied himself with a pile of printed music.

"These things are democratic because they have to be," he said, ransacking the pile for piano quartets and placing them on the music stands in his art-strewn parlor. "It's a combination of ideas and music, but even more, it's a combination of personalities."

Burstein, for one, takes his fiddle-playing seriously (among the cognoscenti, the preferred word is fiddle , not violin ) and usually contends with the flashier first-string parts: "If I practiced three hours a day, the way I did when I was 19, I'd be marvelous."

Before becoming a government lawyer during the New Deal years, he was briefly a member of the Boston Symphony's string section, and now plays about one night a week and practices on his 200-year-old Italian fiddle at every opportunity.

"In a sense, it's the highest form of recreation," Burstein said, baring his bias, "because the people involved are actually creating a work of art together. And what you're creating is coming not out of any individual, but out of the center of the music itself."

At length, the players straggled to Burstein's doorbell one by one. First rang Lisa Frank, a 24-year-old office temporary from Montgomery County. She carried an out-sized cello case, which, when opened, revealed a burgundy-colored instrument from the 19th century.

Then came Ned Davis, 65, an organic chemist from Arlington. A mountain of a man, his lit cigarette hanging on for dear life, Davis skulked into Berstein's living room empty-handed. He would have to make do with the Steinway grand.

Last to show, and late by now (as a matter of tradition, someone is always late), was Gail MacColl, packing a viola. MacColl, 38, works for an educational research organization when she's not playing in the D.C. Community Orchestra.

Burstein pointed everyone to their places. Like an astronaut climbing into a capsule, Davis edged his big frame into the space between the piano and the wall. And then it was down to business.

"Tonight we tune with the pianist," Burstein announced, waving his French-worked bow toward his playing-mate of 15 years. Davis hit a concert A and the others adjusted their pegs.

Then came Wolfgang Amadeus Mozart's G-minor piano quartet, a robust piece that has long been a staple of what, in chamber music circles, is called "The Literature." Davis, a smoking butt on the edge of the piano, his fingers flying lightly across the keyboard, hummed throughout, in a basso that resembled the cello part. Frank and MacColl, eyes glued to the music, pretended not to notice. Burstein chuckled.

"The problem," he said during a breather, "is to get the ideal balance between piano and strings. The lower strings, especially" -- he shot a glance at Davis -- "are often drowned out by the piano."

They went on to finish the Mozart without a hitch. All things considered, a sparkling performance.

"Well, Ned, we haven't played that for a long, long time," Burstein said, wiping his brow.

"Sure haven't," Davis agreed, restoring his glasses, which had slid down his nose during the performance, to their proper position.

Then they launched, with gusto, into Mozart's E-flat Major piano quartet. Davis played and hummed with sensitivity, this time sparking smiles from the cellist and violinist as well.

"Now let's do the Brahms, how about it?" Burstein said, referring to the formidable G-minor Opus 25. "They call it 'The Gypsy,' because of the theme in the last movement.Everybody knows that Brahms wrote it in such a way that everybody thinks he has the solo, so everybody's always going at it hammer and tongs."

"I thought they called it 'The Gypsy,'" MacColl put in, "because when you finish playing, the audience wants you to move on."

"That, too," Burstein sighed. Then he put his fiddle to his chin. "All right, cello," he admonished Lisa Frank, "you start things off, you know."

Frank charged with a few full tones, and soon the room was filled with the lush textures of 19th-century romanticism. The players caught one another's eyes, in search of cues, as they made music. They read on to the second movement, a gypsy "trio" with tricky entrances, and Burstein beamed.

"You're all really doing amazingly well."

Then they came to the majestic third movement, layer upon layer of sound, and Davis, like all pianists confronting Johannes Brahms, got carried away. Burstein put down his fiddle and quietly said, "Ned."

Davis, in a reverie, kept playing.

"Ned," Burstein repeated, a little louder, but to no avail. So he shouted.

"Hey, hey, hey, Ned, Ned!"

That seemed to do the trick. Davis stopped, wearing the startled expression of one awakened from a dream.

"Sorry," he muttered.

Among such amateurs -- which is not to mistake them for dilettantes -- are scientists, doctors, lawyers, engineers: people whose lives demand more than a measure of precision.

Morton Raff, a retired statistician for the Department of Labor, usually plays his violin not once, but three times a week, in informal chamber ensembles. But this is no mere hobby for Raff, who sometimes fears that his "internal metronome is ticking too loudly." These days chamber music is his life.

"My hobby," Raff says, "is collecting roadmaps and scouring them for errors."

A session's appeal might be cerebral for some, especially players who revel in attacking Bach on sight, but a few amateurs like to speak of it as if it were est or jogging.

"It's an intense emotional experience, not unlike therapy," reports Paul Silverman, a Washington clincal psychologist and weekend cellist. "There's something very warm and intimate about it, a sense that very important feelings are captured by the music and must be expressed by the players. . .

"I've often had the experience of playing with total strangers, and by the end of a couple of hours we really got to know one other. There was a communal sense of elation, of being aroused by the music. . . I don't mean that chamber music is a way of coming on. After all, I've never had an orgasm playing the cello."

Another cellist, Jim Lieberman, plays duets with a pianist friend every Wednesday morning. "I think of it as my mental health hour," says Lieberman, a psychiatrist.

Physicians, particularly, seem to be drawn to the pastime in disproportionate numbers, which probably started the rumor that medical schools look kindly on applicants with musical backgrounds.

"There must be some connection, though I'm not sure what it is," says Dr. Oglesby Paul, admissions director of Harvard Medical School. "I myself play the piano."

Because modern chamber music is often murderous as a casual read, pushing most players beyond their limits, the do-it-yourself fare generally turns out to be stuff of at least a century's vintage. A lot of it was created by Europeans of delicate health and sensibilities -- Mozart, for one -- for the pleasure of blue-bloods in their charming little palazzos.

These days it amounts to a blast from the past, but has a sound (whatever can be managed by, say, two violins, viola and cello) as different from rock'n'roll as Dresden china from Tupperware.

David Lloyd Kreeger, the millionaire culture maven, likes to bring out the good china for his musical friends at his stunning manse designed by Phillip Johnson. He seduces them with food and grog, then lures the likes of Issac Stern to his music room. Moving in for the kill, Kreeger boldly unsheaths his Stradivarius.

"My house is like a spider's web," says Kreeger, who also counts among his victims Menuhin, Zukerman and Bernstein.

In Abe Fortas's case, he had judged the matter sufficiently weighty to have firmly discouraged Lyndon Johnson, when he was president, from calling him at home on Sunday nights. Lyndon, remember, used telphones the way most people breathe. But because he knew that his trusted friend would be fiddling with Haydn and Mozart, not even the Leader of the Free World dared to intrude.

And Congressman Jonathan Bingham of New York, who describes himself as a "medium-competent violinist," claims chamber playing can even be used as a vote-getter. During a tough Democratic primary campaign in 1972, Bingham staged a concert/rally at the Bronx's Co-op City housing development.

"We were a great hit," says Bingham, who bowed his way to victory along with members of his family. "Though I do recall, to my shame, that we attempted the opening movement of Beethoven's First Symphony with two violins, cello, flute and clarinet."

That's something like cooking a cassoulet with Campbell's Pork & Beans.