Alt pop darlings Rilo Kiley move away from the rootsy leanings of 2004’s More Adventurous, and go straight for the dance floor on Under the Blacklight, the band’s debut for Warner Brothers.  Some long-time fans may cry “major label foul!” when they hear, for the first time, the polished, full-bodied pop sounds here, but an open mind rewards those who keep the faith. Singer/songwriter Jenny Lewis still charms with her sweet, sometimes plaintive voice, but this time around there are surprisingly deep hooks and dance beats galore. Lewis is a true chanteuse on “Silver Lining” and “Close Call,” with her supple vocals weaving in and out of languid guitars and nearly stealing the show from the gloriously infectious, radio-friendly arrangements. On the panting, undulant track “The Moneymaker,” guitars march along as if in a Modest Mouse song, and “Breakin’ Up” has an aggressive dance beat with ‘70s-styled back-up singers, and, yes, a cow bell. There are tracks that could easily have fit in on More Adventurous, but for something new, move on to Lewis’ soulful and tragic “15,” and to guitarist Blake Sennett’s track, “Dreamworld,” bopping along on a sea of bubbling guitar notes and the perfectly paired vocals of Sennett and Lewis, with the ubiquitous – though subtle – dance beat giving it substance.