Gillian Welch’s 1996 debut, Revival, is one of the era’s most influential albums, its retro stylings and bleak evocations of the dust bowl era marking the transition from alt-country to Americana. Welch’s revivalism was no Carter Family copyism; here was a startlingly good songwriter who could put you in the place of a barroom girl or mountain moonshiner with a few piercing images. David Rawlings’s impeccable picking and harmonies sealed the deal. This 20th-anniversary set fills a bootlegger’s jug with 21 outtakes and demos of Orphan Girl, Annabelle and the rest. The pick of its eight previously unreleased songs are the caustic I Don’t Want to Go Downtown and the homely Wichita, but every drop is delicious.