Megafaun’s Heretofore might be a six-track, written-and-recorded-in-two-weeks mini-album, but it’s got a genuine single. “Carolina Days” comes so loaded with instant nostalgia, it could be a fist-pumping summer amphitheater standard, used in an advertisement by some North Carolina tourism interest or blasted from open car windows all summer long. (Some summer, somewhere, in some universe.) In fact, “Carolina Days” is such a direct, traditional pop song, it’s almost hard to reconcile it coming from the local trioonly almost, though.

For Megafaun, you might call it an experiment, but no less an experiment than anything else on Heretoforeor Heretofore itself, for that matter. The mini-LP also includes the 12-and-a-half-minute centerpiece, “Comprovisation For Connor Pass.” But to brand any of these thingsSouthern boogie or studio gimcrackeryas deviations from Megafaun’s path would be incorrect. In fact, Heretofore is no mini-album. It’s only two minutes shorter than Rubber Soul. More, it’s a real step in Megafaun’s career, full, as always, with modest motion.

As they did (mostly) on 2009’s Gather, Form & Fly, the brothers Phil and Brad Cook and drummer Joe Westerlund lean on the harmony side of the harmony-and-noise formula, but the tension keeps things lively. Though the free jazz saxophones of “Eagle” and the collage electronics of the title track could use far more bite and presence, they represent real territory for the band. “Comprovisation” is especially typical Megafaun. Built from improvisation and layered with overdubs, it remains resolutely consonant and accessible for most of its duration.

If any complaint might be leveled at Megafaun, it’s that they’re too comfortable in their affable center. Even so, perhaps the album’s most jewel-like moment comes with the utterly unexperimental “Volunteers,” a twanging, mournful number with just enough sad notes to keep the song floating through lonesome pines but enough friendly harmony to stay warm. If “Carolina Days” were a real single, “Volunteers” would be its beautiful B-side. Both sides of Megafaunthe experimental and the cosmic American popcontinue to act as equal forces. Ultimately, Heretofore doesn’t satisfy either of those urges in full. Then again, given the scope of those points, it seems unlikely that anything possibly could. That doesn’t mean Megafaun can’t have a long, rich career trying.