Walter WagnerArtist: Black MountainTrack: “The Hair Song,” from Wilderness Heart (due Sept. 14)Label: JagjaguwarRelease Date: It’s out now.Rating (Skip, Stream, Buy): BuyDownload: A sampler pack including track from all of Black Mountain’s records, including Wilderness HeartLocal Show: Black Mountain co-headlines Showbox at the Market with The Black Angels on November 29It would be easy to peg Black Mountain’s recording of such a breezy summer pop single as a sell-out move. In fact, it’s an accomplishment to bring their propulsive psychadelia down to a place where the masses can get a taste without sounding hollow. The result is more southern pop than stoner rock, and that’s just fine. The move — or, at least experimentation– is the opposite of stagnant and the inversion of self-indulgent.Let’s hope “The Hair Song”–meant to played with the top down on I-90 between Missoula and Rapid–is part of collection of songs on Black Mountain’s Wilderness Heart (Sept. 14) that weds the band’s proclivity for California pop with the droning, dusty, psychedelic fuzz that this indie-rock jam band does better than the rest.