The bittersweet mood still lingers: "You must remember this, a kiss is just a kiss . . ." Those words turned Ingrid Bergman's thoughts to romance and may pack a lot of memories for you, too. When the theater is too pricey and disco fever subsides, you can always unwind in Bogart fashion at a piano bar.

All around town there are talented folks tickling the 88s in a variety of moods, from raucous to melancholy. At the Hay-Adams Hotel there's a classy air to the oak-paneled Lafayette Pavillion where you'll find Mike Terrace at the piano. Uptown, at the Royal Warrant on Connecticut Avenue, Alfredo entertains an older singles crowd on electric piano with rowdy show tunes and pop standards. Couples cozy up to a tile-topped piano for soft jazz at C.B. DeMille's in Georgetown. And, across the street at Mr. Smith's, a younger assemblage props gin-and-tonics on the suede-lined bar while swaying to "On and On."

At all these nightspots, the piano sets the scene. Keyboard requests range from Cole Porter classics to Top 40. Stevie Wonder songs turn up as often as "Moon River." At Christie's, Jack Futrell gets a lot of requests for Billy Joel and Barry Manilow tunes. "And they want to hear 'Feelings,' always 'Feelings,' 'Feelings' ad nauseam ," he complains.

Piano bars were actually in their heyday in New York and Florida back in the '40s, but took time to catch on in this area. Washington's first was the Snuggery room at Billy Martin's Carriage House in Georgetown, which led the way for the current roster of over a dozen.

Still the vogue didn't get under way without a fight. The Carriage House piano bar sparked a test case for the ABC regulations in the early '60s. The question was, could they call it a bar? D.C. rules said drinkers had to be seated at a table to be served, but here was an odd-shaped table - or a bar - above a piano top. Eventually officials decided that since drinks weren't mixed at the piano, the Snuggery was legal. The ABC gave Martin a one-year trial period with his novelty - he called the set-up a "piano table." Pretty soon, the regulations were relaxed and piano bars caught on.

What's the fascination?

"We just don't have anything like this in Catalina, California," remarked a loner at the Hyatt House piano bar in Arlington. Explained a regular at the Hay-Adams, "It's a very personal kind of entertainment. The whole audience and the star are only as far apart as the piano top.

Of course, you don't need to know all the words to "As Time Goes By" - nor "Stardust" no "Misty" - to enjoy yourself at a piano bar. Enthusiastic humming is certainly adequate. You needn't have perfect pitch, either. Any key will do, especially after a few drinks.

Behind the ivories, most pianists admit there are ways to fake any request. On a recent night at Christie's, Jack Futrell, trying to accommodate some islanders with "Jamaican Farewell," had to look it up in a songbook and fudge a bit before he could bring it off with flair. He says his batting average on songs he doesn't know is sometimes one in four; still, he has a faithful following of robust double-knits who enjoy his personality plus the backup drumbeat machine.

Piano bar players also develop the knack of answering requests according to the first line or catchwords of a song. They learn to translate "I Like New York In June" into "How About You." Or "Memories" into "The Way We Were." Of course, if they still draw a blank, there's always the standard response: "Can you hum a few bars?"

Most of the entertainers have little or no formal musical training. They concede they've picked up songs from fingering the keys all their lives. All come armed with ragged sheet music and worn out notebooks filled with favorite requests.

One pianist confided it's a job that involves dealing with a lot of lonely drinking people. Romantic melancholia seems a specialty of most piano bars. On the other hand, there's always a number of shower singers who enjoy the chance to belt out a tune in public.

For most listeners, piano bars offer a relaxing change from the sounds of routine bar chatter. "It's a cult thing," says Futrell. "A few years ago you could hardly find any authentic piano bars." Now they're all over the area and waiting to take your requests - unless you want to hear "Feelings."

The Washington Hilton has an elaborate setting for Jean Packard and her grand piano in the center of the Point cocktail lounge, the Prime Rib has a beautiful glass-topped grand and The Roma has a pianist you can sing with during dinner hours - they are pleasant in their own way, but none of them counts as a piano bar in the strict sense. The following sampling includes only authentic piano bars where you can sit around the piano, look directly at the player, swirl your ice and pitch a request.