Smithsonian Folklife Festival participants, interns and staff close out the first week of the festival with a dance party at the Key Bridge Marriott in Rosslyn. (Sadie Dingfelder/FOR THE WASHINGTON POST)

Night has fallen along the banks of the Potomac. Across the river in Georgetown, people are pouring out of movie theaters, dancing in bars, staggering down sidewalks. In Rosslyn, the only sounds are the groan of an empty escalator and the whoosh of cars as they fly past dark office buildings and chain hotels.

But inside the charmless ballroom of the Key Bridge Marriott, an international battle of the bands is taking shape, pitting traditional European folk musicians against the drumming descendants of escaped slaves. This is the after-hours entertainment for an eclectic group of performers — men and women who’ve gathered from around the world to enliven the Mall with music, art and dancing at the Smithsonian Folklife Festival. Think of the Marriott, then, as a kind of folklife Olympic Village, temporary home to exotic dancers, throat singers and speakers of rare tongues.

“They told us that there’s no nightlife here” in Rosslyn, says Jeffelyn Baltazar, who is among those who seem determined to create their own.

“The Hungarians, they never stop singing and dancing,” she observes, her voice croaking after a day of giving presentations on the Mall. The rasp doesn’t stop her from chatting in rapid-fire Spanish with her new friend Andris Julio, a musician from Colombia, who pulls up a music video on Baltazar’s smartphone where he raps in Spanish and Palenquero, a South American language with about 500 native speakers. Baltazar tells Julio that she also speaks a rare language: A native New Yorker, she is a member of a small ethnic group known as the Garifuna, who descended from escaped slaves who intermarried with Carib Indians.

More than a hundred Hungarians who’ve spent the day teaching tourists how to do circle dances in 90-degree heat seem determined to defy jet lag and continue dancing well into the night. An acoustic string band lays down a mighty wall of sound for dozens, who separate into groups of four and wheel around the room. Subtle signals that the party should wind down — hotel workers turning down the lights, removing the food, closing down the bar — go unheeded. A heavyset woman walks around and tries in vain to persuade people to go to bed, pressing her hands together beside her tilted head — the universal pantomime for sleep.

Baltazar takes a tentative step into the ballroom, then retreats as a pair of Hungarians fly past. At the other end of the hall, her fellow Garifuna are gathering, though: A Garifuna band from Los Angeles sits with backs pressed against pale-yellow wallpaper and hands resting on goatskin drums.

The Garifuna go almost unnoticed as one Hungarian tune stops and another begins without so much as a whisper of silence between them. Suddenly, a wiry man with Medusa hair makes eye contact with his California bandmates, then fires a warning shot to the Europeans across the ballroom: a set of quick triplets played on a big bass drum. Two coltish Hungarians turn in surprise. The big drum sets a steady pulse, and the smaller drums join in with syncopated rhythms.

Volume-wise, the Hungarian band is no match for the Garifuna.

Dancers gravitate toward drummers, and Baltazar materializes at the center of the circle. She crouches low to the ground, arms akimbo, her bare feet a blur of movement. Julio looks on as a cheer rises. Unlike the Hungarian string band’s tunes, which followed a strict hierarchy, this is music that everyone feels comfortable contributing to. Tables, guitar cases and at least one turtle shell are pressed into percussive duty. A Native American flute trills atop the driving beat, and a musician from the remote region of Russia known as Tuva plays a pair of metal spoons.

This moment of multicultural harmony is interrupted when the band tries a call and response. The crowd can’t decipher the Garifuna syllables. Some say, “Hey!” Others yell, “Eye” or “Day.” But when the band yells, “The roof, the roof, the roof is on fire,” the crowd responds in near-perfect unison.

Not everyone is happy about the cultural switch. “I could have listened to the Hungarian music all night,” an American volunteer mutters. And a long-limbed Hungarian woman, her hair in intricate braids, starts to tap, distracted, on a cellphone. Two men in khaki pants retreat to the hallway with their fiddles. They lean in close to each other and trade flurries of notes.

The woman looks up from her phone, and a violist joins the duo. Soon the entire Hungarian band has reconstituted in the hallway, and a dance circle is beginning to form.

A little farther down the hall, three Hawaiians sit on the plush carpet singing a plaintive song about love lost, and a Tuvan throat singer adds a didgeridoo-like sound to their crystalline harmonies.

When Hungarians begin to dribble back into the ballroom, it seems clear that the Garifuna band has decided to call it a night. Four members, drums balanced on their backs, head toward the elevator.

Have they conceded to the Hungarians?

“Yes, they win,” says Garifuna drummer Shaka Higinio. “I can’t tell if it’s the same ones who are always playing or if they are taking shifts.”