Even Steve Earle admits that by the time you’re in your fifth decade of writing songs, inspiration can be tough to find. Then came an invitation by Shawn Colvin, the Grammy-winning singer-songwriter. In late 2014 she asked Earle to join her for a week of shows together. Unlike most twin bills where two songwriters swap songs onstage, Colvin and Earle discovered that besides sharing a common folk root in their music, when they sang together it created a perfect blend.