The cumbia beat serves as the many-faced god of music: when properly applied, the stutter-step triplet is an assassin on the dance floor and can mold to any genre. To invoke this deity of a rhythm, Cumbia Fest rallies three masters of the form. El Rebelde del Accordeón, Celso Piña (pictured) is a pioneer of cross-cultural cumbia, fusing ska, reggae and hip-hop styles. Together since childhood, Coahuila’s Grupo Massore forays with a casual grace into pop and funk. At 69, saxophonist Fito Olivares is a fixture of tejano and cumbia in the Valley, gaining his energy from the play between rhythms.