Iron & Wine’s calm folk-rock demanded peace and quiet, and for the most part, got it from a very polite crowd. Backed by a band that, akin to its leader’s razor-repellent facial hair, seems to grow with each passing month, frontman Sam Beam looked freshly aroused from a long nap. The group never detoured from the sleepy pace, relying on wood-block percussion and pedal-steel guitars to patiently trek through the sonic equivalent of the Amazon forest. At first glance, Iron & Wine’s lullabies seemed a tailor-made match for playing to parents and children over on the nearby Kidz Stage. But seedy matter lurked underneath the otherwise tranquil exteriors of “House by the Sea” and “The Devil Never Sleeps.” And their soothing moods and hammock-sway slowness encouraged a few adult pursuits — joint smoking, beer sipping, tripping — still off limits to the stroller set. Yet the muted aura occasionally dragged, a risk taken by any band traveling in the direction of a more strung-out version of the Grateful Dead.