Over the past 20 years, this New York outfit, led by Juan "Juango" Gutierrez, has been on a mission both to preserve and to revitalise the music of Puerto Rico. Los Pleneros De La 21 brings together players, singers and material, old and new, while keeping alive some of the music's less fashionable aspects, including folk dance forms such as Bomba (dating back to the 1600s) and Plena (from at least a century ago) from which the ensemble takes its name. Musicians who play for the Plena dance are pleneros. The instrumental sound is highly rhythmic but the beats are warm and caressing, making for a music that is always energetic but rarely aggressive.

The vocals are shared between singers such as Nellie Tanco and Hector "Tito" Matos. Angel "Paco" Vazquez makes a telling appearance on trombone on numbers such as Carmelina and Madame Calalu, a portrait of 1950s life in the barrio. Chiviriquiton, another old number, is updated to include a rap, in English followed by tongue-twisting Spanish, while Isla Nene is a protest song prompted by the US navy's occupation of (and eventual departure from) the Puerto Rican municipality of Vieques. Yet whatever the content, the dancing continues. The rhythm of the barriles de bomba, panderetas, timbal, maracas is quite unstoppable.