After two acclaimed self-written "folk operas" (Hadestown and Young Man in America), Vermont-born Anaïs Mitchell sidesteps into deep tradition. The antique British ballads gathered by the 19th-century professor Francis Child have been a wellspring for modern folk, whether delivered straight (Anne Briggs) or twisted into new shapes (Fairport, Emily Portman). Mitchell and Hamer keep things simple, acoustic guitars embellished by touches of fiddle and organ but relying on close vocal harmony to drive narratives of shape-shifting lovers (Tam Lin), unwanted pregnancy (Willie of Winsbury") and doomed aristocracy (Sir Patrick Spens). With archaic language updated by transatlantic twang, it's a winning addition to the canon.