In 2017, the Vocal Vidas, an all-female Cuban quartet, were invited to perform their first show in America. Complicating the trip was the fact that relations between the U.S. and Cuba, which had somewhat opened up under President Obama, were rapidly closing down again under the new administration. What began as a concert became a journey across physical and ideological borders: an affirmation of the connective power of music, even in the most uncertain times. “Soy Cubana” efficiently provides a grounding in the lives of the four charming members of Vocal Vidas, who struggle to keep the group going because there’s so little money to be made from performing in Cuba. The opportunity in LA — made possible by an invitation to perform at the city’s Grand Performances summer concert series — is thus a significant validation for the quartet. These insights into the women’s backgrounds are welcome, but the group’s performances undeniably provide the film’s high points: Although not a concert film, “Soy Cubana” very effectively presents full performances of many songs in the group’s repertoire, and the women’s complexly interwoven voices are truly transcendent. The film was the deserved audience-choice winner in the 24 Beats Per Second sidebar of this year’s SXSW.