Many groups performing traditional folkloric music are overly reverential and quaint, but not Los Pleneros de la 21. Appearing at the Smithsonian Folklife Festival on the Mall Sunday, this large South Bronx ensemble turned the Sounds of the Forest tent into a culturally hip dance hall. With a Puerto Rican flag draped over a drum, lyrics about their homeland and nonstop rhythm, they made traditional music vibrant.

The group is named after a bus stop in a San Juan neighborhood that was home to many plena and bomba musicians. Los Pleneros have not only kept those two Afro-Latino genres alive, they have updated them lyrically and musically. On bomba numbers such as "Angelito," Julia Loiza, resplendent in a blue flowing dress with yellow headwrap, took center stage and danced to a skittering beat from three barrel-shaped drums, a barrel that was hit with sticks and various hand-held percussion instruments. Thanks to catchy call-and-response vocals and keyboard and bass accents, these lengthy compositions also jelled into songs.

On the plenas, the band substituted oversized tambourines, called panderetas, for the big drums, and added the guitarlike strumming of the cuatro. While they used sentimental vocal melodies on most of the plenas, for their adaptation of "Chiviriquiton," the combo seamlessly inserted a rap interlude. Closing with the standard "Que Bonita Bandera," the unit gleefully strode back and forth across the stage, chanting and banging on their drums with the aid of clapping and singing from the dance-floor crowd.

-- Steve Kiviat