It was fell and he'd finally been cured disco fever. He'd strutted his stuff and rocked around the clock and boogie-oogie-oogied 'til he dropped. He'd grown tired of his John Travolta white suit.

So he found himself in the smokey rathskeller, hunched over a beer mug and looking bleary-eyed at the corner bandstand. There were no amps, flashing lights or turntables, nothing to remind him of the downtown clubs where he'd hustled and jumped and twirled to blaring Bee Gees. Instead there stood a piano, a string bass, some horns and, in the background - whatzat? - a tubs. A hulking brass tuba. He took a long drink from the glass and blinked.

After a while, some middle-aged men in red-and-white shirtsleeves began to leave their seats at nearby tables and shuffle over to the bandstand. They remainded him of those GS-14s normally hidden in the bowels of regulatory agencies. Slouches and paunches and glasses, hoo-boy. They gingerly stepped onto the stage and moved behind the instruments to regard the half-empty house with yawns. With the right choreographer, they could have been the original models for the Lonely Hearts Club Band.

But the banner draped over the piano read "The Riverside Ramblers," and the six posed ready to play. Without a word, the keyboard man began laying down some bouncing chords and without a cue the others followed. Suddenly the band was erupting with the sassiest version of "Sweet Georgia Brown" he'd ever heard: The trombone growling out the deep-down bass notes, the clarinet spinning forward licorice-sweet frills, the trumpet sliding along the register without a care in the world.

From his perspective on the rim of the beer glass, he watched the over-the-hill gang burn the heart out of every refrain. He smiled. His fingers snapped. His feet started an uncontrollable tap dance under the table. He felt transported to a bistro in old New Orleans as the music took hold. And he laughed out loud. So this was Dixieland.

Dixieland Jazz. The words alone conjure visions of honky-tonk street life. Brewed in the bars and brothels of Storeyville at the turn of the century, traditional jazz has spent its life hanging on from minor renaissance to minor renaissance in large cities dotting the country. It's never won popularity contests against the more current styles of jazz and never stolen a crowd from classical or rock or even country-western. No club owner has ever made a fortune by sticking a Dixieland front line under the spotlights.

But - thanks to nostalgia - traditional jazz has continued to cling to the fringes of mass appeal and in the '70s is again enjoying a resurgence. This area alone boasts 18 bands that play regular gigs at clubs and restaurants in Washington, Baltimore and Annapolis. The thousand members of the Potomac River Jazz Club (PRJC) crowd local dance floors to swing and cakewalk to the uptempo rhythms. The air waves of several FM stations regularly vibrate with the tunes of Count Basie and Bix Beiderbecke and Jelly Roll Morton - sweet sounds, indeed.

Fact is, The Nation's Capital has become one of the hottest outposts for Dixieland this side of the Mississippi. And this Saturday the current, followers of old-time jazz will celebrate at the 8th Annual PRJC Jazz Picnic, to be held at Blob's Park in Jessup, Md. A dionysian blow-out, the affair features a truckload of beer and 14 bands playing nonstop from noon until long after the stars look bloodshot. Jazz fans have always turned out en masse , with families and picnic baskets and lawn chairs, to settle back for the festival of music and brew. "Usually, by the end of the evening, everyone ends up pretty soaked," says PRJC president Dick Baker cheerfully.

It's a fitting end to the festivities. Almost singlehandedly, the PRJF has kept America's true musical form thriving along the banks of the Potomac with its formula of brass and booze. In 1971, five jazz-lovers kicked in $50 apiece to print a newsletter detailing who was playing, where and when. Interest spread faster than you can say "Bill Bailey." Virginia's jazz buffs wanted to meet Maryland's jazz buffs, and vice versa.

Today the PRJC has 700 families, and ever-growing roster of top-flight jazz bands and enough collectors to provide the 78s for a 90-minute weekly radio show on WPFW, "Jazzband Ball." Its members include accountants, military men, historians and a lot of white-collar workers who seem unlikely candidates for Dixie fever. Senator S.I. Hyakawa, California Republican and a jazz critic in his own right, joined the club after sitting in on piano during an evening PRJC jam session. Channel 7 weathercaster Sam Allred entered the rolls when he showed up at last fall's jazz picnic with a trombone to ward off the rain. It worked.

For $10 a year, members get the monthly newsletter filled with tidbits on local jazz artists and a calendar of performance dates. The PRJC also holds periodic musical happenings, like the picnic, that specialize in live Dixieland and strong drink. There's a New Year's Eve bash coming up and a riverboat cruise down the Potomac every spring.

Once a month, the club takes over the Bratwursthaus in Arlington for an open jam session, where closet musicians who haven't touched their instruments since college drag out their tarnished horns to sit in for a set or two. They sign up to play as they come through the door, trumpet players under one heading, trombonists under another. Then the first six troupers march to the bandstand to start the songs flying. The madness goes on all night.

"Jazz has never prospered professionally in Washington," says Dick Baker, a Russian linguist for the VOA when he's not talking jazz. "There have always been amateurs who located each other for jams in somebody's basement or put together bands to play one night a week in a pizza parlor. But Washington has never had a full-time professional jazz band like New York or San Francisco or San Antonio. And the simple fact is that the music is not commercial enough to pay for itself."

Certainly the PRJC has done a lot to improve this state of affairs. Nowadays PRJC-affiliated bands can be heard seven nights a week around town. You can choose between ragtime piano at II Porto Ristorante and New York revival jazz at the Rockville Shakeys. Local acts have adopted names with hometown appeal, like the Federal Jazz Commission, the Original Crabtowne Stompers and the Washington Channel Jazz Band.

And sooner or later, the bands end up at the Bratwursthaus, headquarters for the PRJC, in a glass-and-neon shopping center off Wilson Boulevard. With its plastic figurine elves on the walls and silhouettes of jazz musicians in the windows, it's difficult to tell whether the Bratwursthaus is closer in ambience to Bavaria or Bourbon Street. The menu features schnitzel. The bandstand offers stomps. The common denominator seems to be the pitchers of beer.

Del Beyer, 55, has been leading the Riverside Ramblers Thursdays at the Bratwursthaus for serveral years. A retired Navy officer with graying hair and wicked fingers on the keyboard, Beyer first heard jazz as a teenager tuned to the Chicago radio stations playing Sidney Bechet, Lena Horne and Dinah Shore. In 1975 he showed up at one of the PRJC's monthly jam sessions and became inspired to start his own band, initially called the Anacostia River Ramblers. But "The original name seemed to give the wrong impression," he says, so the band started calling itself the Riverside Ramblers and playing at Northern Virginia clubs and restaurants. And Beyer became the piano-playing bandleader.

On stage, he directs the ensemble with a genial, laissez-faire attitude. He'll introduce a tune with a brief remark - "Here's a low-down blues tune called 'Tin Roof Blues'." And then the band will slide into the song with deceptive ease for the complex interplay. During the lead breaks the men take over the limelight with the passion of virtuosos, arching their backs, closing their eyes and twisting their instruments into the spirit of the sounds. "Personally, I get sort of high from performing," comments Beyer.

To say nothing of the audience of club regulars who watch the show with beery concentration. Couples take over the dance floor to do the Charleston or the black bottom or the two-step. There's a lot of table-hopping and spouse-swapping on the way to the dancing. Before a song is over, people have usually applauded the musicians, the dancers and, occasionally, each other. It becomes difficult to sit still under the spell of the hootchie-kootchie numbers and the Roaring Twenties rags.

So the ex-John Travolta lookalike eventually found himself on the dance floor with a local fox by his side. And he started to move subconsciously into the spins and dips that had seen him through a hundred nights under a disco mirrored ball. His partner looked at him with bemusement. She was swinging the way they used to do it in Saint Louie, and a clash of cultures seemed at hand. He paused while the band played on until gradually the beer took hold and fogged his disco memory. He began to shimmy with the rhythm and high-step to the beat. Form be damned, he couldn't help but laugh along with the music. This was Dixieland.