Demanding of recognition but ever pushing back at attention, Stephin Merritt is a droopy-eyed Marlon Brando of art pop. A notoriously difficult interview, the singer-songwriter is prone to epic pauses and blank stares, and even his shyness can come across as condescension, which makes him a rough subject for a documentary profile. Yet that dissonance is also what makes Strange Powers, a 10-years-in-the-making record of Merritt and his Magnetic Fields bandmates, so intriguing. A fuller picture of Merritt does come into view, especially in terms of his longtime friendship and musical collaboration with Claudia Gonson, the affable, earthy yang to Merritt’s urbane yin. But after a tantalizingly idiosyncratic beginning—Merritt shows off his ukulele collection and instructs Gonson on how to play kitchen whisks as percussion—directors Kerthy Fix and Gail O’Hara proceed with a perfectly fine but disappointingly by-the-numbers rock doc, obliging us with tasteful portions of rehearsals, performances, modest beginnings and major breakthroughs. Ideas arise from the proceedings—about music making, mythmaking and ambition—but the film doesn’t pursue them. In the end Merritt remains studiously opaque; he’s most present when affecting a self. He writes, sings, and performs in character, and remains the Chihuahua-carrying bard of the West Village even after relocating to Hollywood.