IT'S 10:30 on a Tuesday night and Freddy's, a rather nondescript restaurant and tap room at Connecticut and M, is all but deserted, except for one young couple engrossed in conversation at a table near the door.

"Do you have a reservation?" Selma Sims inquires, mock-seriously, as I take a seat at her left, at the piano bar, under the Tiffany lamp. Selma Sims is a woman of mature years - blondined, strong-featured, and dressed in black with gobs of gold jewelry. The artist in residence.

"I've been playing since nine," she confides with a sigh. "It's a very slow night . . . very unusual." She frowns. "It's never this slow . . . ."

She gives me an appraising look. "Are you a singer?" she asks. Not lately, I tell her. "Oh, why don't you sing," she cajoles. "We get some fine singers in here, some wonderful voices. The Paris Opera was in here . . . would you believe? I sing very badly myself," she adds. All this time she is rambling through her repertoire, playing oldies but goodies like "Guess Who I Saw Today" and "Rain" and "Pennies From Heaven."

A waitress appears. I order a Heineken. "Any requests?" she asks. "Anything the customers ask for, I play. What's your favorite song, your favorite of favorites?" I name a favorite. She hesitates. It's not one of hers, it appears. She does a few arpeggios to get her bearings. "'Emily' . . . let's see," she says, trying to remember, "haven't played that one in years . . ." Gamely she has a go at it, with some prompting at the bridge. I'm sorry I didn't ask for "Tea for Two." Then she does "Laura."

How many songs does she know, I ask. "Oh, thousands," she replies. And her favorite of favorites? "This is one of them," she says, and goes into "Angel Eyes." Then comes "Tenderly."

She's been playing here seven years, she tells me between numbers, "I was all over town - Anna Maria's, Mr. Henry's, Bassin's, Alfio's -" she ticks off the places. And now Freddy's. "My little corner of the world," as she describes this red oblong room with the silver trim we're sitting in. Originally from Philadelphia - "my father played first trombone with Bunny Berrigan," she notes with some pride for her show-biz heritage - she moved here with her husband "oh, a long time ago," more years than she cares to count, she indicates. So much for biography.

More customers drift in after a while. First, a middle-aged man in a trenchcoat, obviously a regular, and obviously looking for more company than he finds in here tonight. He stays for one drink and leaves. Then an older threesome show up, two men and a woman, out on the town, sort of. They've never set foot in Freddy's before, even though they live "around the corner." They went to Fitzgerald's (another piano bar near Dupont Circle) but it has closed, and . . .

Selma Sims takes it in stride. They're nice people, for all that."What's your favorite song, your favorite of favorites?" she asks. One of the men, an older banker type, wants to hear some World War I songs. Music to Selma Sims' ears! Immediately she rips into "Over There" and "It's A Long Way to Tipperary," and then "Rose of Washington Square." Then she does a good, leathery, talk-sing rendition of "Hard-Hearted Hannah."

"They don't write 'em like that, anymore, do they?" drawls the vamp of Philadelphia, Pennsylvania, as she finishes with a flourish. The banker type is tickled. So are the others. So am I, for that matter.

By midnight the young couple has left, but the piano bar, at least, is well populated. Mostly older types. And when one tipsy woman decides we all should shake hands and introduce ourselves to each other, I know it's time to pay the check and leave. Besides, Selma Sims, after three hours of playing, has taken a "five-minute break." What better time to make a graceful exit?

It was not to be. "You're leaving," she admonishes, looking up from a conversation with a gentleman at the barstool. "You should stay. It really starts to pick up about now . . ."

So it would seem. But I've had enough of this instant memory lane for the geriatric set. And I'm wondering as I head out the door and up Connecticut Avenue toward home - is this the prototypical piano bar in town? Bobby Short, where are you now that we need you?

Then again, I guess I'm operating under a delusion: piano-playing in a bar is supposed to be this vaguely disreputable but inherently romantic occupation, awash in chic nostalgia and errant glamour. Or so the movies would have us believe, anyway - movies like "Casablanca," where Dooley Wilson turns to the keyboard in the smoky, war-torn atmosphere of "Rick's" and starts warbling "You must remember this . . .," calling up painful, wonderful, imperishable Paris memories for Bogie and Ingrid Bergman.

Not to mention "Shoot the Piano Playes," Truffaut's homage to Warner Brothers gangster movies. Who could forget that long closeup fadeout of soulful anti-hero Charles Aznavour, the concert pianist on the lam, sitting there in that seedy Paris bistro, playing that odd little tune on that battered, tinny-sounding piano. The very embodiment of early-Sixties existential angst, and all that.

But the movies do tend to lie to us about things like this - or at least exaggerate. Probably no piano-player in real life is as charismatic as, say Warren Beatty in "The Only Game In Town," oozing boyish charm as the compulsive Vegas gambler-piano player, pitching love ballads, and woo, to disillusioned chorine Elizabeth Taylor. Or for that matter, as piteously bad as Ellen Burstyn, the hard-luck widow in "Alice Doesn't Live Here Anymore," getting leered at by drunks and propositioned by psychotics in a dingy Tucson dive as she segues, madly, from "Where or When" to "When Your Lover Has Gone" to "Gone With the Wind." You want a more convincing real-life example from the movies? Well, maybe it's the fat, raunchy lady in Robert Altman's "California Split," banging out the numbers with more gusto than precision. Now there's a recognizable type. Take it from me.

A few nights later I make a stop at Mr. Smith's a pseudo-Gay-Nineties Georgetown pub which bills itself as "the friendliest bar in town." I only stay for a few minutes. I am really repulsed by what's going on in here - loud, bad, obnoxious amateur singers with hand-mikes, committing vocal mayhem on songs like "Carolina in the Morning" and the ubiquitous "Feelings," while Bernie Bury, the hapless pianist, struggles manfully to accompany them. Incredibly, some of the people sitting around the piano seen to be enjoying it.

My next destination is the lounge of the Embassy Row Hotel on Massachusetts Avenue near Dupont Circle, where I find Judith Kenez, a dramatic-looking Hungarian chanteuse, trying to entertain a motley collection of moneyed out-of-towners - including some tweedy-looking Kentucky horse-breeders - with intimate, sophisticated songs in the "Falling In Love Again" - "La Vie En Rose" vein, and wryly amusing repartee. That she is only fitfully successful is no reflection on Kenez. She is charming, and talented, and obviously too classy an act for this ornate yet tacky barroom. A showcase it is not. And she makes no secret of her disdain for the inattentive boors assembled here tonight:

"Some of them think I'm somebody over there making noise in a corner," she tells me during a break. "I could be Sammy Davis Jr. and an eighteen-piece band and they wouldn't wake up!"

It wasn't like this in Europe and South America, she says, where she was a well-known nightclub entertainer and proprietress before she married "a colonel in the American Army" and moved to Washington in 1961. She is now divorced and has two grown children.

"The other night there was a man, a very loud man, from Georgia, who sat very close to the piano," she relates. "He kept calling me 'Baby' and 'Honey' and I finally told him, 'I am too old for such names. Please, give me the honor to call me Judith. And he apologized. He was sorry. He was a gentleman. A gentleman who drinks is still a gentleman," she explains, "but a peasant who drinks is still a peasant - and you can quote me!

"There is only so much you can do," she adds philosophically. "When they are terribly loud I just ignore them and play 'Fascination.'"

"No way I would ever let them put microphones in here," says Ken Foy firmly. "They'd start carrying on like Mario Lanza. It would be torturous."

Foy knows what he'd talking about, and he should - he's the chief exponent here of sing-along, and he appears nightly (except Sundays) at the Robin Hood Lounge and Restaurant at 14th and K Streets. "The incomparable Ken Foy," as his ads say in the entertainment guides. An affable Larry O'Brien type with an easy, ebullient playing style, Foy goes a long way back in the Washington music business - big bands, supper clubs, combos, and, for the past seven years, solo piano. Foy is very good at coaxing disparate groups of people - businessmen, tourists, suburban housewives, secretaries, foreign students, ladies of the evening, what have you - to join in and sing the old familiar favorites, even when they don't know all the words. His approach , he readily admits, is less sophisticated than some, more participatory than most. "That's why people come in here," he says, "so they can be a part of the act."

He's not exaggerating, either. The Saturday night I ventured down to hear him, Foy had barely warmed up the assembled handful of would-be songsters when in walked two pleasant-looking young couples from the suburbs. Regulars, obviously. As if on cue, Foy played an introduction and one on of the women launched into a sweetly inspirational rendering of "Climb Every Mountain." Her husband and the other couple stood behind her, off to the side, smiling indulgently. The woman finished to a generous round of applause. Thus encouraged, she encored with "Danny Boy." More Irish songs followed. And corny jokes. And more requests. And a lot of good-natural, light-hearted banter. It was all very much like a suburban Saturday night "sing" around the old upright piano - the kind the Birch Bayhs are said to enjoy in their rumpus room - only this was a downtown bar, and a Steinway, and a seasoned professional in charge of the festivities. Which does make a difference.

Another seasoned professional is Mel Clement. So seasoned, in fact, that if anyone deserves to be called the grand old man of piano bar playing in Washington it would have to be him. You're immediately aware you're onto something very good, even quintessential, when you walk in the door of the elegant Georgetown Inn on Wisconsin Avenue and hear these smoothly rhythmic sounds emanating from the Restaurant, right off the lobby. It's Mel and string bass player Louis Saverino, doing their thing with a newly minted pop standard called "What I Did For Love" from "A Chorus Line." A good omen, it would seem. Who says all piano bar players dwell exclusively in the musical past? When a good new song does come along, it's nice to know some of them are with-it enough to get it into their repertoire.

Mel's a large, grandfather, tuxedo-clad gentleman with crinkly eyes and thinning, slicked-back hair. Super-genial, and so expert at what he does that he can feed you bits of his biography before, during, and after a number from his seemingly limitless repertoire, which ranges over the whole pop-jazz spectrum and back again.

He, too, goes a long way back in the music business - some forty-five years. He was part of the big-band era and the heyday of radio. He's done TV, accompanied singers, led orchestras, and he teaches piano and composes. He's been playing in the chandeliered splendor of the Four Georges for five years. Before that it was the Snuggery in Billy Martin's Carriage House a block down the street - "the first piano bar in Washington," he notes, "and a test case for the ABC board. back in the Forties and Fifties, you know, they were sort of illegal - they had to charge you for a glass of water of water and an ice cube," he adds, breaking up at his own little joke.

His is easily the most scintillating piano. I've heard in a cocktail lounge in Washington. It's very slick. Maybe too slick. Some say Mel Clement is very cynical in this regard, programming himself for surface effects. he could dig deeper.

But then the clientele in here hardly inspires that Painted ladies and their well-heeled alcoholic escorts, weaving grotesquely on the dance fllor, loudly demanding "When the Saints Go Marching In" over and over again feigning poses of studied indifference. The ambience is alienating and I leave as soon as Mel and Louise take a break.

I heard down a block to the Snuggery, a posh, dimly lit, dining-drinking backroom in the Carriage House where I was the night before - for several hours, listening to John Eaton weave his magic spell. This is my kind of piano bar. The mmod is cheerful low-key, attentive, alive. Nobody striking attitudes

There at the piano is Eaton, a fortyish scholarly looking Yale grad and native Washingtonian, poring over some sheet music. By ironic coincidence it turns out to be "What I Did For Love" from "A Chorus Line." A nuisance lady the night before kept nagging him to learn it. He said he would. "Come back tomorrow night!" he instructed with mick severity. I thought he was just mollifying her, but here it was, tomorrow night, and a new group of people, and Eaton is giving the Marvin Hamlisch ballad a tentative run-through, adding Eatonesque touches here and there, getting the feel of it, deciding that yes, it really is a pretty good song, isn't it . . .

No less an authority than George Shearing recently said "John Eaton is the best piano player in Washington," an accolade Eaton accepts with his usual modesty.

He has a quietly contagious love for the music he's playing, be it Gershwin, Porter, Loesser, Sondheim, the Beatles or Ravel. But just when you think you have him pegged as a "cerebral" solo pianist, he'll switch moods and hit you with some funky Art Tatum or Fats Waller blues numbers, complete with raspy, low-down vocals. And he was playing Scott Joplin long before "The Sting" made ragtime the rage again.

One ley fact stands out abput Eaton: Despite myriad distractions - everything from drunk women falling off the barstools to non-stop talkers and would-be satyrs looking for "action" - he manages to keep it a listening ezperience in here. Music values do prevail.

"It's an act, in a sense," Eaton says, "but its extremely flexible. Its not a concert. people like it because it isn't a hushed concert-hall atmosphere. Theylike the camaraderie of the bar, and they like recognition - they's terribly important. But when you don't want to play some of their song requests you have to be terribly careful not to stay the wrong thing. You don't want to offend them, or make it sound as though you're questioning their taste. People have these very secret antennae . . ."

"John absolutely refused to play 'Born Free' and 'Ebb Tide,' says Penny Eaton, his piquantly pretty young wife, who comes in to hear him two or three nights a week, and has been known to seek out a far corner of the Snuggery and crochet when the amateur-night ambience gets too thick.

"In the course of an evening you can see the whole mood change several times," says Eaton. "You can start with a serious group, and then very suddenly somebody will latch on to something you do . . . the important thing is to work them arounf on your terms."

Like tonight, for instance. There's another nuisance woman - a raucous. red-haired Angela Lansbury type and, it turns our, Cole Porter freak, who announces she wants to hear "You're The Top." Lyrics, too, if you please. "You're the top, you're the tower of pizza . . . c'mon, John," she cajoles. Eaton says she doesn't know it. Will she settle for "Anythong Goes"? Yes, she'll settle, but only because that's an "up" song, too, and she only wants to hear "up" songs - "up" Cole Porter songs.

"Cole Porter went through twenty-eight operations on his spine," she informs us, with something like evangelical fervor, "and he wrote 'up' things. Fantastically inspiring: I believe it!"

There are bemused glances all around. There are three other men, two women, and the lady's escort, a solid looking Greek man in a navy chalk-striped suit, who remains silent.

Eaton moves into one of Porter's best ballads, "From This Moment On." It's messerizing, but not for the raucous redhead, "Do some more 'up' songs," she commands. "Do 'Mame.' Do 'Dolly'. . . how about 'Cabaret'"?

"Okay," says Eaton.

"Oh, grand!" exclaims the redhead lady, tapping in rhythm and singing tunelessly along, not unlike a regular at the Kit Kat Club.

Eaton, answering another request, does "Send in the Clowns." It, too, is mesmerizing, nut not for the redhead lady.

"Oh, another sad song," she groans. "Wgy do you play such sad songs?"

Other customers plead with her to be quiet, but the redhead goes on. Two scotches. Three scotches. The other guests want to listen as Eaton launches into Ellington. They say so. But she won't leave it alone. "Play happy songs," she implores again. "C'Mon, John . . . 'You're the top, you're the tower of pizza . . ." Eaton continues with Ellington. "John," she says, after a moment, trying for an apologetic tone and not quite succeeding, "I've given you hell tonight, haven't I, John, disrupting you every song . . . "

Eaton, the soul of tact and a very tolerant man says nothing. But he's had enough of this loud-mouthed dame, it's clear to see. He takes a break and turns on the Muzak. A soft trickle of a sing is heard overhead. It is definitely not an 'up' number by Cole Porter.