What does it take for a work of art to become an intervention? In music, any reinterpretation alters the original, if only because different fingerprints touch it. But certain lineages — folk music, for example — are built on the bones of those retellings. Whoever owns a song for a period of time connects it to her lived experience and the world in which she lives, and it changes. It might also change the world, or a small part of it.