Alison Krauss has the voice of an angel. You probably heard her on the Academy Awards singing a track from Cold Mountain or on the wonderful soundtrack for O Brother, Where Art Thou? where she sings the heart-breakingly beautiful Down to the River to Pray. She plays with the versatile Union Station whose I am a Man of Constant Sorrow was also featured in O Brother. For more, Alison Kraus + Union Station Live is an excellent place to begin.