If the rock-inflected energy of Aterciopelados' 2006 album, Oye, was a response to the more electro-pop avenues the band had found itself wandering down beforehand, then this year's Rio stands as further proof that the Colombian group's grasp of organic, muscular pop remains one of its strongest attributes. Though somewhat more relaxed than Oye (and, in places, somewhat more predictable), Rio also comes across as a much more seamlessly collaborative effort. In the run-up to Oye, both of the group's principals — Andrea Echeverri and Hector Buitrago — released solo albums. Echeverri's richly textured disc and Buitrago's glitchy electronic foray resulted in influences that were at cross purposes for some of Oye's tracks. On their first album since then, the group's internal balance seems restored. It must be noted that, after more than 15 years of touring, the members of Aterciopelados have definitely matured. There's a midtempo vibe that dominates much of the material on Rio, which does a disservice to songs like "Gratis" that, though energetic, should be crackling with a dangerous electricity that never fully shows up. Another downside of maturity: the need to craft a heart-tugging singalong like "Ataque de Risa," complete with a chorus of kids. That said, the vast majority of Rio's 13 tracks — most notably "Treboles," "Hijos de Tigre," and "Bandera" — find Aterciopelados at their quirky best, piling spaghetti-western guitars, soundboard trickery, and a raft of other touches atop political-pop numbers that are as heartfelt and well-crafted as they are loose-limbed and concert-ready.