In Metric, Emily Haines specializes in glossy, synth-centric pop. In her occasional stints as one of Broken Social Scene’s many vocalists, she shows she can rock out. On her solo albums, though, she favors melancholy, thoughtful piano ballads. Choir Of The Mind, her third, is a showcase for Haines’ delicate, careful voice; it’s serious and artful without being heavy handed (as long as you don’t mind a lengthy spoken-word passage from an Indian mystic poet). Whereas she fleshed out 2006’s Knives Don’t Have Your Back with strings and horns, here she’s assisted only by Metric bandmate James Shaw (and, on one track, Sparklehorse drummer Scott Minor). The focus is on the vocals, and Haines often layers her voice into lush backing choirs. The outlier is “Fatal Gift,” which, with more glitz, could be a Metric track; as it is, it’s the album’s most extroverted moment, with dense layers of harmony vocals and a tense rhythm track. But Choir Of The Mind is more often introspective and engrossing.