Gillian Welch, the Los Angeles-raised musician, whose lyrics and voice conjure Appalachian hollows, Dust Bowl highways, and Nashville morphine dens, released her first album, “Revival,” twenty years ago. Several of the songs sounded as if they might have been written a hundred years earlier. Welch’s alto is rich and tarnished, with a roughness that hints at a tired or heat-baked throat. In “By the Mark,” she promised, “By the sign that shines / Upon His precious skin / I will know my savior / When I come to Him / By the mark where the nails have been.” Welch wrote from the perspective of the type of people the folklorist Alan Lomax had sought out in the nineteen-thirties and forties—poor, usually either exploited or forgotten—whom Lomax and other revivalists saw as carrying organic traditions of sound, feeling, and imagination. In “Annabelle,” a poor sharecropper whose young daughter has died reflects, “Till we’ve all / Gone to Jesus / We can only / Wonder why.” Other songs on “Revival” were first-person laments, confessions, or boasts from moonshiners, migrant fruit pickers, and bootleggers.

Four years earlier, Welch and her musical partner, David Rawlings, had finished their studies at Boston’s Berklee School of Music and moved to Nashville, which at the time was closer to the sequined industry town that Robert Altman sent up than to the spirit of the Stanley Brothers, Bill Monroe, and other icons whose memory Welch and Rawlings had followed south. None of the singer-songwriters on the Americana scene—Guy Clark, Nanci Griffith, Steve Earle—sounded as old, or as fresh, as Welch. In a 2004 Profile by Alec Wilkinson, Welch and Rawlings described themselves as nocturnal loners in those years, playing music in the silence between the last flight into the nearby airport and the first birds of morning, or just wandering quiet streets in a town that then closed early. They played open-mike nights and attracted the attention of the veteran producer T Bone Burnett, who produced “Revival.”

The Times wrote that the album “doesn’t strike a false note.” But, from the beginning, enthusiasm for Welch’s music was cut by skepticism about the woman who played it, the adopted child of Hollywood music writers, who had spent part of her early twenties in a psychedelic surf-rock band at U.C. Santa Cruz. The Rolling Stone critic Ann Powers complained about Welch’s “handcrafted simulacrum of rural mysticism.” To Wilkinson, Welch described the first time she heard bluegrass recordings, in college, as a chill-down-the-spine epiphany, “like an electric shock.” All the careful artifice seems an effort to do justice to a feeling that these are the sounds she should make.

In Rolling Stone, Powers judged that “Welch never takes the risk of wondering what her own experience might bring to the tradition.” Welch’s second album, “Hell Among the Yearlings” (1998), mixed ragged, banjo-driven mountain ballads with slow-moving laments in a way that mainly carried forward the out-of-time mood of “Revival.” Then, in 2001, “Time (The Revelator)” squarely answered complaints about Welch’s purer-than-the-originals anachronism. In “Revelator,” emblems of American loss and catastrophe—Elvis’s death and John Henry’s, Lincoln’s assassination, the sinking of the Titanic, the Okies’ flight from the Dust Bowl—are braided with close observation of contemporary derelicts and charismatics. The album’s unity resembles a primitive style of Biblical exegesis, in which the preacher points to a Bible passage, then to something that happened yesterday, and declares, “This is that which was spoken.” Lincoln, John Henry, and a never-launched punk band whose ailing and stoned members Welch meets in a gig parking lot become instances of the same thing—which is never quite named, except as “ruination.” Echoing the prophet Ezekiel, Welch sees “a wheel within a wheel,” hears “a call within a call,” while watching a waitress on a slow-moving morning.

With “Revelator” and later albums, such as the sweetly eclectic “Soul Journey” (2003), folkloric sources became pliant elements in a style. Listening to the music is no longer like dropping in on the past. Welch sets out autobiographical details with seeming documentary candor, including fragments of her time in college bands and her erratic classroom performance in the years when “We were riding high / Till the eighty-nine quake / Hit the Santa Cruz Garden Mall.” With debts and allusions to Gram Parsons, Steve Miller, Neil Young, and Townes van Zandt, and to blues, folk, and gospel, Welch and Rawlings treat all of American music up to the time of their childhoods as a folk culture. They often sing in the “brother music” style of harmony associated with the Stanleys and the Everlys, which creates the illusion of a single voice, with just a glimmer of separateness that leaves the sense of unity flickering and uncanny. Welch’s voice still moves between bell-ringing and husky intimacy, and Rawlings’s guitar is both languid and precise. The sound holds moods the way humid air holds smells. Being lonesome and listless is often both the topic and the feeling, but the songs also carry a pleasure in the achievements of their flat, sometimes bleak exactitude. The two-piece outfit called Gillian Welch may be lost in the world, but it is fascinated by the wrinkles and motes of that experience, and has found the notes for them.

Welch takes from her mountain and Southern sources a set of metaphysical intuitions. We are not made for satisfaction. To be a person is often to feel exiled, alone, and predestined. These axioms of Appalachian Protestantism, which you can hear in songs like the Stanley Brothers’ “Rank Stranger,” are the fixations of Welch’s “The Harrow & The Harvest” (2011), her fourth and most recent album, whose master theme is fatalism. “The way that it goes,” “the way that it ends,” and “the way it will be” are some of the refrains, and the music feels like being caught in a slow-moving but irresistible force, maybe just the temperamental force of what Welch calls being “blessed with a dark turn of mind.” The predestination here is to perennially reckon with unruly and obdurate feeling: people cannot help what moves them, what makes them feel alive. Morphine, “soldier’s joy,” and heroin pop up frequently in Welch’s songwriting, and, like other motifs, feel as much symbolic as literal. The sense of fate in her mature songwriting resembles the feeling of addiction: a blurred line between desires and needs, pleasure and enervation, what feeds you and what consumes you.

Maybe it is unsurprising, in a musician of consummate aesthetic discipline, that Welch sometimes seems drawn to dissolution, a personal “ruination.” Her narrators are often at the end of their roads, going invisible, asking to have their legacies dismantled. “Tear my stillhouse down” is the last instruction of her moonshiner on “Revival,” and in “I’m Not Afraid to Die” and on “Hell Among the Yearlings,” she looks toward a future where “Every work of my own hand / Be broken by and by.” The happiest and most relaxed I’ve seen her onstage was in Boston in 2007: she was touring with Conor Oberst (playing with Bright Eyes), whose band had turned the theatre into a wall of noise from which no identifiable note escaped. Welch held a tambourine and was leaping with ungoverned delight, shaking her instrument in wild sweeps, with no chance at taking responsibility for the sound. It was, for a few clamorous minutes, an end to her labor.