In 1972, long before O Brother, Where Art Thou? allowed hipsters and intermittent record buyers through the great oak doors of traditional country music, California's Nitty Gritty Dirt Band gathered legends and soon to become legends of country music into a Nashville studio and made the sprawling Will the Circle Be Unbroken. The success of this experiment led to a second volume in 1989 and a third in 2002. Trilogy compiles all three worthwhile volumes into a box set that includes the extra tracks found on the recently reissued versions. With a roster that includes Doc Watson, Maybelle Carter, Johnny Cash, and Taj Mahal, this 40-year time capsule of American music is worth spending the extra cash on.