Mining Studs Terkel territory, the second installment in Daniel Kraus’s “Work Series” (sandwiched between 2006’s similarly eponymous Sheriff and next year’s Truck Driver) is an hour-long vérité peep into the labors of you can only guess what occupation. We first meet the film’s unassuming subject, a goateed fortysomething named Ken Vandermark, as he sits in a Chicago basement studio trying to compose a piece of music entitled “Mirror Values.” He blows his saxophone, gets frustrated, tickles some ivories, scribbles some notes, and the next thing you know he’s on a stage, going passionately nutso and discordant, because he is, in fact, a well-known jazz improviser. Kraus cites vérité godfather Frederick Wiseman as an inspiration, and while there’s a taste of stylization in the editing—split-screen, out-of-sequence reveals, superimposition—Musician is a fairly pure work, or what Werner Herzog would dismiss as “an accountant’s truth.” The “truth” is that touring isn’t all that glamorous, and neither is watching Vandermark return calls, schedule gigs, eat fast food, and check in/out of hotels that all look alike. At one point, the musician declares that his existence “is starting to feel like Spinal Tap.” Maybe if we’re talking lumbar punctures.