What song did bob dylan perform with mumphord and sons and the avett brothers?

Bob Dylan took part in a multi-song suite that included Mumford & Sons' "The Cave," and with the Avett Brothers' "Head Full Of Doubt, Road Full Of Promise."

Tags: the avett brothers,  mumford,  bob dylan,  sons 
Monday, February 06 2012
Source: http://www.pastemagazine.com/articles/2011/02/bob-dylan-avett-brothers-mumford-sons-performing-t.html