As an interpreter of folk songs, Sam Amidon is as fearless as they come. His repertoire, plucked largely from the kitchens and front porches of Appalachia and his native Vermont, maintains a fingerpicked core, updated with his own melodic phrasing and subtly shifting rhythms. But the real reinvention is in Amidon’s delivery: plainspoken vocals that dryly turn songs filled with assumptions about morality and faith into modern provocations. Here, he performs with masterful jazz guitarist Bill Frisell and multi-instrumentalist mainstay Shahzad Ismaily behind a new disc, Lily-O. Amidon opens for Wilco at the Riv the previous evening.