Like Bob Dylan did in the mid-‘60s, Gillian Welch and David Rawlings joined with a rhythm section on 2003’s Soul Journey to record some of their most indelible songs. Cut from an analog master and pressed for the first time to vinyl by the duo’s own label, Acony, the album’s 15th anniversary reissue offers a beautiful way to revisit a landmark of contemporary folk music. Though the “two-person band named ‘Gillian Welch’” (as the pair have long described themselves) had gone electric before, and would do so again (mostly in their Dave Rawlings Machine spin-off), Soul Journey shines brightest when the pair plays unaccompanied, a solemn and assured setting for Welch’s ghost of a voice and Rawlings’s sublime lead guitar. Paradoxically, perhaps, the album’s opening track and the closest the two have come to writing a modern standard, “Look at Miss Ohio,” is not among these, with drums emerging metronomically like someone’s idea of how to perk up their perfectly gothic Americana. The duo’s last album as “Gillian Welch” for eight years, Soul Journey makes it hard to tell where the folk adaptations stop and the original songs start, as on “No One Knows My Name” (an original, with the gentle addition of banjo and fiddle) or “I Had a Real Good Mother and Father” (traditional, with new lyrics by Welch), whose lyrics echo one another. Soul Journey makes it equally hard to tell where the past ended and the present began, or remember why anybody ever thought there was a difference.