Home Jambase Jason Isbell & The 400 Unit Debut Allman Brothers Band Cover In... National Music NewsJambaseMusic Jason Isbell & The 400 Unit Debut Allman Brothers Band Cover In Seattle September 13, 2017 228 FacebookTwitterPinterestWhatsApp Rockers Jason Isbell & The 400 Unit worked up a cover of an Allman Brothers Band song for last night’s show in Seattle.