“20 Feet From Stardom” may possibly be the happiest time you’ll have at the movies all summer, but it comes with a heavy load of frustration. The joy — and at times it’s absolutely transcendent — is in the sound of women singing their big, beautiful hearts out. The pain comes from the anonymity they’ve spent their lives working under and fighting against.
Until now, anyway. The movie’s the latest rock-archeology documentary project, where the spotlight gets cast, finally, on artists you don’t know but should. It’s a rich genre, and recently it has delivered affecting human stories like last year’s Oscar-winning art-house hit “Searching for Sugar Man,” which made a long overdue star of singer-songwriter Rodriguez.