Now that the entertainment industry lies in ruins, music has retreated to its old haunts—the bars, halls, and yard parties where players hypnotize the locals. So says Chris Strachwitz in This Ain’t No Mouse Music, and he’d know. He’s spent more than 50 years seeking out groundbreaking but unheralded American musicians in places that few people, even those scouting for the industry in its most powerful days, had any real idea existed.

Strachwitz is the man behind Arhoolie Records, the small but essential independent label founded in 1960 and committed—feverishly, evangelically committed—to documenting the music of rural southern highways and fields, especially in Texas, Louisiana, and Mississippi: gospel, country blues, conjunto, zydeco, Cajun, jazz, bluegrass, Moravian brass, on and on, recorded live in all their gnarled brilliance by Strachwitz, on the spot with only a mike and an occasional camera crew.

This Ain’t No Mouse Music is full of these mesmerizing performances from the past half century, with Strachwitz’s chuckling, gangly presence always hovering at the edges. The man himself is a one-off, born into the Polish gentry and exiled to the States as a teenager at the end of the Second World War, where he fell in love with the songs coming from the family radio.

That love is clear and total, and beams from Strachwitz’s face whenever music he admires is playing and he’s tossing out a heartfelt “gawl-dang” in an accent that still bears faint prints of Europe. And he’s equally transparent when listening to the music he professes to loathe, the so-called “mouse music” of the title—his contempt-soaked term for anything he considers too timid or eager to please.

A scene in which Strachwitz heckles a band he’s decided he dislikes at a small folk festival, making meow-ing noises from his folding chair just a few feet from the stage, is both hilarious and excruciating.

But any instant of sourness is no match for the joy, ferocity, and defiant wit that flows from Arhoolie recordings of once-neglected masters such as Lightnin’ Hopkins, Mance Lipscomb, Bukka White, Big Mama Thornton, Clifton Chenier, and Lydia Mendoza. This warm documentary tribute to Strachwitz is a kind of victory lap around the South, an act of meta-preservation—preserving the now-aged preserver. And as it’s sure to drive attention back to the musicians themselves, it’s merely the next step in his long, wayward, beautiful mission.

Cinematheque, May 4 (6:45 p.m.)