Whether you want to call it Americana, roots music, folk or something else, Gillian Welch has been at the forefront of it since she first emerged 20 years ago with Revival, her T Bone Burnett-produced debut album. It seemed to come from another time and place—the plaintive voice and simple picking, words that could just as easily have been sung in 1920s Appalachia as 1990s LA: “I am an orphan on God’s highway/ But I’ll share my troubles if you go my way/ I have no mother, no father/ No sister, no brother/ I am an orphan girl.” Boots No. 1 revisits that debut: Its two discs of outtakes, demos, alternate mixes and live recordings don’t so much suggest a reimagining of as a path deeper inside. As on the finished, official release, Welch is accompanied throughout by multi-instrumentalist/vocalist David Rawlings, who has been integral to her music ever since. Their chemistry is already evident on the rough song sketch of “Acony Bell,” which closes out the program, and the alternate take of “One More Dollar,” minus the backing instruments that Burnett would add to the album track (using heavyweights like James Burton and Jim Keltner). As for the outtakes, several are quite good, but it’s difficult to imagine, with two decades of hindsight, any of them having made the original album any stronger than it already was. Boots No. 1 (which, as its title suggests, is only the first in a series) isn’t so much a way of saying here’s what could have been as a reminder of something that was perfect the way it was.