The surprise companion to the National's April release, First Two Pages of Frankenstein, is the band's most freewheeling, all-hands-on-deck album in years. If Frankenstein represented a rebuilding of trust between group members after 20-plus years together, the vibrant, exploratory album is both the product of that faith and a new statement of intent. Reveling in the license to radically upend its creative process, the National honed most of this...