Filmmakers Chris Simon and Maureen Gosling both worked with the late documentary legend Les Blank, and they obviously share his unpretentious enthusiasm for indigenous American culture. Simon and Gosling’s new film profiles another such enthusiast, Arhoolie Records founder Chris Strachwitz, who for more than 50 years has been tracking down and making records of the humble grassroots music that most excites him. This could be just about anything — Delta Blues, Cajun, Tex-Mex, Appalachian — as long as it’s not the mainstream stuff Strachwitz refers to very pejoratively as “mouse music.” Here the avid traditionalist comes across as a generous talent-spotter, but also a prickly heckler — he knows just as well what he doesn’t like. Simon and Gosling don’t provide specific examples of mouse music, possibly because those rights clearances would have been too expensive. Also, well, they called their movie This Ain’t No Mouse Music, borrowing a line from Strachwitz himself, and would prefer to champion the good stuff. As interviewee Davia Nelson of NPR says, “It’s the music of your neighbors, you just don’t know it.” Lots of other journalistically conscientious testimony is made available — from the likes of Ry Cooder, Bonnie Raitt, Taj Mahal — but the music’s importance also is obvious just from how good it feels to hear it.