Though he lacks the poetic inspiration of Les Blank, D.C.-raised Robert Mugge (shown here with Jack Owens during the filming of Deep Blues) has made more than a dozen important, if straightforward, documentaries about American music and culture on the fringe. Like Blank, he’s an unabashed fan of his subjects, but Mugge’s films often come off as sober-minded promos rather than insightful profiles: True Believers: The Musical Family of Rounder Records (Dec. 15, 6:30 & 8:45 p.m.; the director will be present) tells the story of the Massachusetts-based independent label that has rescued and sustained so much vital music—from Jimmie Rodgers to Michael Hurley—during the last 25 years. A bunch of hippies getting rich while staying true to their mission should have made for a captivating tale; instead, the film—featuring yawner interviews and boring concert footage—has all the fire of an NPR feature on how to make money peddling Cajun music. (Yeah, there’s a decent cameo by Gaithersburg’s much-missed Johnson Mountain Boys, but that doesn’t make up for the insufferable folk preenings of Bill Morrissey.) True Believers shows with Pride and Joy: The Story of Alligator Records (Dec. 16, 4:30 p.m.; Dec. 20, 8:15 p.m.), Deep Blues (Dec. 17, 8:15 p.m.; Dec. 21, 6 p.m.), and The Gospel According to Al Green (Dec. 20, 6:30 p.m.; Dec. 22, 7:30 p.m.) at the Kennedy Center’s American Film Institute Theater. (202) 785-4600. (Eddie Dean)