Though the breathtaking vistas of Big Sky Country in Ilisa Barbash and Lucien Castaing-Taylor’s unforgettable sheep-herding documentary come close to heaven, it’s telling that AC/DC’s “Highway to Hell” can be faintly heard over the sound of the electronic contraptions that hired hands yield to shear the docile creatures, one of the preparatory stages before the round-up begins. A record of the last time, in the early aughts, that cowboys led their flocks up into Montana’s high summer pasture, Sweetgrass captures the arduousness and the awe (not awww) of a vanishing way of life. Animals strike curious poses: One of the white, fluffy sheep stares right into the camera as the film begins, a moment played not for critter cuteness but for ovine empathy, immediately setting the patient, unsentimental, observational tone. Sweetgrass reminds us of the stupefying magnificence of its setting—beautiful for spacious skies and mountain majesties—while never letting us forget its formidable perils. (NR) MELISSA ANDERSON

Fourth Thursday of every month, 8 p.m. Starts: June 23. Continues through Nov. 24, 2011