Peeking out of the shifting atmospherics of Lower Dens’ sophomore album, Nootropics, is a furtive intelligence that teases the listener with glimpses of hidden worlds and conflicted emotions. Frontwoman Jana Hunter guides her group a bit deeper into electronica terrain this time out, fusing the evocative austerity of Brian Eno’s late-‘70s productions with the opiated haze of modern shoegaze bands. Hunter’s cool (but not disengaged) vocals murmur over gliding tracks that interweave vintage synthesizer sounds, arid beats, and guitar feedback washes. “Brains” sums up much of Lower Dens’ bewitching appeal with its cinematic jump-cut lyrics and ominous groove. The jittery rhythm of “Alphabet” and the darkly swelling contours of “Lamb” further define the band’s ability to construct subtle soundscapes out of minimal elements. The undulating bass and echoing vocals of “Propagation” add an unexpectedly sensuous touch. Elusive but mesmerizing, Nootropics haunts the mind after the last note has faded away.