This is my earworm, my sad anthem for happy days of friends and Detroit beauty. The harmonies are perfect, expected Mumford. The lead is Oscar Isaac who I know better as Poe Dameron, X-wing pilot from the new Star Wars. It's an old song collected in 1934 from a woman named Dink who sang it while washing her clothes in a river. It's a ballad of longing for a lover departed across the river to Arkansas, leaving the speaker pregnant with his baby. Whatever river of time or space or circumstance separates us, dear reader, fare thee well.