Folk giant Pete Seeger has been honored so universally for his contribution to protest music, it’s easy to forget the details of his importance. But be careful: Reconsidering his life story could make you feel awfully ineffectual by comparison, even if you have written a song as significant as “Turn! Turn! Turn!” Cutting between archival performance clips and recent interview footage (Seeger is now 88), the action in this biography feels more like a high wire than an arc. Swaddled in one of the 20th century’s greatest songbooks, the film is a new essential for folk enthusiasts and an inspiration to anyone who strives to live beautifully.