Over the past 20 years, Wilco have gone from plain-spoken alt-country to the pinnacle of experimental folk and art rock. Hear how that happened on this four-disc rarities set, which is often so raw it feels less like opening the vault than rooting around under Jeff Tweedy's bed. Hyper-low-fi demos of songs like 1995's "Passenger Side" show the first signs of the wry lyricism that blossomed on later albums. Even better are a trove of unreleased cuts that peek at alternate realities – check "Unlikely Japan," a mellow, trippy flip side to the 2007 live favorite "Impossible Germany." Taken together, it's a comprehensive document of a great band with endless secrets to reveal, even now.