Every musical-footnote band eventually gets the documentary it deserves, and this ragged, affectionate chronicle suits the forgotten acid-folk curio combo whose screechy “If You Want to Be a Bird” somehow made it onto the Easy Rider soundtrack. (Recall Jack Nicholson flapping his arms on the back of Peter Fonda’s chopper, then don’t rush over to iTunes to download the track.) The Holy Modal Rounders were an early-’60s product of the Greenwich Village folk scene, pre-Dylan and pre-Beatles. An appearance on Laugh-In (included here) is about as far as they ventured into the mainstream. Though he played drums with the group, Sam Shepard has to be reminded of that TV gig. “What kind of drugs were we on?” he asks. Uh, basically all of them: Founding duo Peter Stampfel and Steven Weber are today serious acid casualties who parted for most of the ’70s, then reunited in the ’90s. (Among the highbrows who helped spark new interest was Yo La Tengo, which covered “Griselda” on Fakebook.) Still, watching the Rounders re-form and rehearse is mostly painful in a Crumb sort of way. Weber is a wreck, living in a ruined Pennsylvania farmhouse with his poor octogenarian mother. Though you’d never want to hear his yowling for more than one song, Stampfel eventually cleaned up and married late in life. When his tween daughter cheerfully explains how her celebrity-obsessed classmates say her dad’s music sucks, neither she nor Stampfel seem remotely perturbed. Even without a melody, persistence counts for something.