Recorded in Nashville and produced by Peter Collins, the album's arrangements have a down-home feel and reflect both the Girls' Southern roots and their love of Appalachian and bluegrass music.

The band, all amazing players, includes Alison Brown on banjo, Victor Krauss on bass, Luke Bulla on fiddle, mandolin and guitar, Jim Brock on percussion, and Lloyd Maines on dobro and pedal steel.

Sacred and secular, traditional and original, the tracks reflect the ecumenical spirit of the duo's diverse fan base, from Chely Wright's "It Really Is (A Wonderful Life)" to Woody Guthrie's "Happy Joyous Hanukkah," with Janis Ian and Mary Gautier on background vocals. Some songs include a third harmony part: Julie Wolf added guest vocals on "I'll Be Home For Christmas" and Brandi Carlile harmonizes on several tracks. The album also features the Indigo Girls' arrangements of such classic Christmas recordings as "Oh Holy Night," "I'll Be Home For Christmas," and "Angels We Have Heard On High" as well as three original (and instantly classic) songs written by Amy and Emily - "Your Holiday Song," "Mistletoe" and "The Wonder Song." Holly Happy Days is a long overdue love letter to the holiday season by these iconic vocalists.