The It's Complicated star, who is also an award-winning bluegrass banjo player, and What I Am hitmaker Brickell have recorded 13 tracks together for a new release called Love Has Come For You.
The singer says, "I fell in love with the banjo tunes because at first listen they evoked images and stories that were true to me."
And Martin adds, "The banjo can be so evocative when it's used sparingly, and that was in the back of my mind as we were writing. It's the way I've longed to play and hear the banjo, rather than it being present at every moment. In these songs, the point is to tell the story and get out."
The album, which will be released in April (13), also features Esperanza Spalding, guitarist Waddy Wachtel and Nickel Creek stars Sara and Sean Watkins, as well as members of Martin's bluegrass band the Steep Canyon Rangers.