***Across its first two LPs—2008’s Bury the Square on Table of the Elements and Gather, Form and Fly, the band’s Hometapes debut—MEGAFAUN did nothing if not test the boundaries of its comforts. JOE WESTERLUND and brothers BRAD and PHIL COOK found rarified intersections between bedrock folk and howling drone, between primal blues and cascading feedback, between canyon rock and warped field recordings. Heretofore, a mini-album and Megafaun’s third release in as many years, is yet another articulation of the band’s evolved Americana vernacular. Rather than push the boundaries with sonic plundering or structural pillaging, however, Heretofore finds Megafaun pairing five of its most concise, communicative songs to date with its most challenging, compelling experiment ever, a radiant and redemptive 13-minute instrumental called “Comprovisation for Connor Pass.”