“Failure is a very creative place,” asserts James Nicola, artistic director of New York Theater Workshop where singer-songwriter Anaïs Mitchell and director Rachel Chavkin developed their flamboyantly successful Hadestown, a folk opera based on the Orpheus myth. But is failure really so useful, or is it just, well, failure? Rachel and Anaïs consider that question, describe the quailites of a good local bar, and report on the whereabouts of Smoke, the lost-and-presumed-dead cat. And yes, they sing. Gloriously.