As one of the most prominent bands of early '90s rock en Español, Aterciopelados (which translates as "The Velvety Ones") refuse simply to sit back and enjoy the fruits of their labor. On their latest disc, Río, they urge fans to support the struggle for the recovery of the Bogotá River — one of the most polluted in the world. The '70s-rock-inflected "Bandera" tackles the immigration debate, looking at the situation of undocumented aliens while criticizing the U.S. government's current position on the matter. Recently, the band collaborated with various world-music artists on "The Price of Silence," an Amnesty International single written in celebration of the 60th anniversary of the Universal Declaration of Human Rights. The catchy tune has Aterciopelados' signature sound — a mix of Colombian cumbia beats with smart, funky guitar riffs that they call vallenato eletrónico, which could arguably be considered a subgenre of the group's own creation.