“A squid eating dough in a polyethylene bag is fast and bulbous. Got me?”

Welcome to the mind of Don Van Vliet, a.k.a. Captain Beefheart. That quote, from 1969’s otherworld masterpiece Trout Mask Replica, opens the “independent critical analysis,” Captain Beefheart: Under Review, and, in a way, epitomizes the career of a man who, without exaggeration, did more to challenge the limits of popular music than any other artist of his generation. It makes no sense and the image is a bit disturbing, if not flat-out disgusting; same goes for Van Vliet’s music, a sort of mutant blues with no discernable forebear nor — stylistically at least — any direct descendents. But, like the thought of a squid gorging itself on cookie dough, the experience of hearing a Beefheart record for the first time is a hard thing to shake. And the more you think about it, after a while, it attains its own kind of absurd logic.

Under Review, released on DVD on April 25, attempts to explain that logic for the uninitiated in typical rock-crit fashion: an album-by-album dissection of the Captain Beefheart discography, presented by a panel of biographers, journalists and the ever-revolving cast of musicians Van Vliet enlisted to translate his ideas into sound. It’s a losing proposition. While the film works as a surface-level overview of Beefheart’s metamorphosis from a Rolling Stones clone into a surrealistic Mississippi Delta swamp creature, it fails to dissolve even a shred of the mystique clouding his legend. Van Vliet himself appears only in the rare, often bracing live footage that buffers the talking heads: mustachioed, with deeply lined skin and wide, darting eyes, gesturing like an end-of-days preacher and declaiming in a voice like Howlin’ Wolf holding a belt sander. After 1982’s Ice Cream for Crow, he retreated into the avant-garde art world and is currently somewhat of a recluse, living in Northern California and reportedly suffering from multiple sclerosis.

In his absence, it’s left to the ex-members of his supporting group, the famed Magic Band, to offer insight into the bizarre creative process that generated the fractured classics Safe As Milk, Clear Spot and the aforementioned Trout Mask Replica. Here is where the documentary achieves a certain level of revelation. Not a traditional musician by any stretch, Van Vliet’s method of composing was at once completely alien and utterly simple: He’d describe each part to his sidemen in terms of natural sounds — windshield wipers in motion, an ashtray hitting a wall, twirling shopping bags filled with random objects. As cacophonous as the final product often seems, it was always intricately arranged and furiously notated, and nearly everyone who played with Beefheart testifies to having their perception of songwriting forever altered.

And that’s the “magic” referred to in the band’s name: Van Vliet’s ability to transform the nonsensical into the unquestionable, and to show anyone daring enough to keep listening a new perspective from which to see, feel and hear the pop song form. It takes a certain amount of diligence to be able to answer the “Got me?” at the end of the beginning statement in the affirmative, but the reward is one of the truly singular recorded histories in the rock canon.