Banjo magus Béla Fleck might be the poster boy for such musical curiosity. Opera superstar Renée Fleming also enjoys a boundary-defying inquisitive streak. The seemingly odd bedfellows have surrounded themselves with an A-list cast of bluegrass musicians, including mandolinist and singer Sierra Hull , bassist Mark Schatz and guitarist Jake Stargel. His warm, perceptive fiddle provides commentary, harmonizes with Hull and Fleming and occasionally steps out beautifully on its own. These songs speak of longing, of grief during war and the sturdy hope for better times to come.