What makes Bill Callahan a mesmerizing performer? He has two expressionsone shyly, slyly neutral, the other a stanky guitar faceand two stage moves. Sometimes he prances a little, like a kitten marching on a duvet, and sometimes he adds a sort of “move away from the mic to breathe in” maneuver, like in “Chocolate Rain.” At his Duke Performances show Saturday night, he told two stories, an incomprehensible bit about a man in tiny running shorts and a dig at a local nightclub that shall remain nameless, because I have to live here.

Otherwise, Callahan stood still and stoically played his acoustic guitar on the stage of Baldwin Auditorium. Electric guitarist Matt Kinsey sat over a rack of pedals, scraping his pick and riding the whammy bar, embellishing Callahan’s patient wood grain with glistering squalls.

Callahan is not really an Americana musician; he’s a sphinx in homespun. But lyrical, quietly virtuosic musicianship formed a through line with the opening set by modern traditionalists Nathan Bowles, who occasionally let loose his rusted brass voice but mainly provided popping, rolling drumming, and Jake Xerxes Fussell, who led with his sincere, lonesome singing and his sweet touch on a borrowed Gibson SG.

Callahan ranged widely through his eponymous work, from “Jim Cain” to “Drover,” with a couple of beloved ringers from his last Smog record, A River Ain’t Too Much to Love, for good measure (“Say Valley Maker,” “Rock Bottom Riser“). But all gravitated toward the epical vortex of his last two albums, epitomized by a slowly apocalyptic “America.” I confess I could have stood 10 percent less extended harmonica techniques overall, which unbound the spell of his deep, even baritone and implacable guitar.

But you can’t stop progress. Callahan’s songs are about change, and the songs themselves are changing. Virtually no trace remains of the tenor voice from his early days; if he ventures the high notes at all now, he does so very softly. His songs are becoming less ingratiating and more profound, each at once lasting a million years and ending before you know it.