It’s a good day for aggressively brooding Chicago instrumental rock. First came word the Windy City quintet Del Rey has seen its album sales jump in Germany — never mind if it’s mostly thanks to coincidentally named pop seductress Lana Del Rey. Now comes a new track from fellow atmospheric Chicago heavies Pelican since 2009’s What We All Come to Need. “Lathe Biosas,” from the upcoming four-song EP Ataraxia/Taraxis (out April 10 on Southern Lord) marches confidently between art-rock foreboding and neo-metal churn, all in less than five minutes. The title is Greek for “live unnoticed,” but why?