Thursday, (Dec. 11) Vince Gill, Chris Hillman & Herb Pedersen and Daniel Lanois have been added to the lineup for the event, which will be held at DAR Constitution Hall.

Previously announced acts include Harris, Mavis Staples, Kris Kristofferson, Joan Baez, Sheryl Crow, Lucinda Williams, Conor Oberst, Alison Krauss, Trampled By Turtles, Steve Earle, Patty Griffin, Rodney Crowell, Iron & Wine, Shawn Colvin, Shovels & Rope, Sara Watkins and The Milk Carton Kids.