Forro, simplified, is a dance form and its attendant music that, for over a century, has been extremely popular in northeastern Brazil, its profile having been considerably raised by the late folklorist and accordionist Luiz Gonzaga. Forro is generally played with three instruments — the accordion, the zabumba (a bass-like drum), and a metal triangle — although younger bands have updated the style by using electric guitars, more modern percussion, and other contemporary instrumentation. Forro in the Dark are not Brazilian but rather a sextet from New York City where, since 2002, they’ve packed in the dancers at the downtown club Nublu by expanding and urbanizing the sound. Bonfires of São João is their debut, and it becomes clear rather quickly that their relationship with traditional forro is nominal. Forro in the Dark hang on tightly to the danceability of the music but are keen to expand the music’s sonic parameters. A reggae tune, “Limoeiro do Norte,” spotlights a wobbly flute up front, while “Que Que Tu Fez” crosses an insistent Afro-Caribbean rhythm with flamenco handclaps, a flighty flute, and a spry vocal. Guest stars liven up the proceedings: David Byrne vocalizes exuberantly on two tracks, including “Asa Branca,” a forro standard, and the Brazilian diva Bebel Gilberto donates a rich, sultry lead vocal to the airy ballad “Wandering Swallow.” Miho Hatori of the band Cibo Matto further blurs the lines by bringing a Japanese pop taste to Gonzaga’s “Paraiba,” originally recorded in the 1950s. – Jeff Tamarkin