While social and political issues are not new to the music of this Colombian rock duo formed by Andrea Echeverri and Hector Buitrago, Rio is actually the first time they effectively bring forth a call to action for a cause close to their hearts: on the title track, which (as Texans oughta know) translates as "river," they urge fans to support the ongoing struggle for the recovery of the Bogota River, now considered one of the world's most polluted. However, activism is not Rio's sole theme. Echeverri also celebrates new life on "0328," a happy reggae whose title refers to the date she discovered she was expecting her second child (during their recent European tour, the vocalist went onstage with her belly proudly exposed — as of this writing, she's still expecting). The duo also gives its take on the immigration debate with "Bandera," a ska track whose poignant words look both at the situation of undocumented aliens who seek better lives for their families and the current administration's position on the matter, repeating the chorus "Que quien es usted / Que donde nació / Entonces no puede entrar a esta nación" ("Who are you? / Where were you born?/ So you can't come into this country"). Rio is one of Aterciopalados's best works in recent years. Perhaps because they were not distracted by solo outings — Echeverri released her self-titled CD in 2004, while Buitrago put out Conector two years later, around the same time the duo's Oye came out — they were able to give themselves fully to the new project, with extremely positive results.