Ethereal, spectral, and absolutely gorgeous, AIA: Alien Observer was easily one of 2011's finest releases. Yet what genre do we stick this woozy and slowly evolving stuff into? Is it experimental or alternative rock? It’s hard to find an act as purely interested in experimentation and melody with equal measure. No matter what you’re doing when you first hear music by Liz Harris (a.k.a. Grouper), after a few minutes it’s hard to not find yourself doing nothing but listening. It has that kind of intense, vacuum effect, drawing you in. Take a song like “Moon Is Sharp,” where layers of reverb swim atop a sea of echo, slowly unveiling a gently strummed electric guitar and a pretty singing voice. The way the slowly reverberating sounds morph from abstract pleasure to pop bliss and then smudge themselves back into an ambient smear is surprisingly cathartic. It sounds good, too.