In last year’s New Yorker profile of Ralph Stanley, bluegrass star Ricky Skaggs, who used to play with Stanley, offered this insight into the legend’s longstanding appeal: "He’s become like an old African, a world-music person." What he meant by that, it seems, is that Stanley is now an artifact from a lost time and place — a beacon of so-called authenticity who defies questioning and critique. Like the proverbial "old African," Stanley, in Skaggs’s opinion, has been around so long that he’s ossified into someone who deserves only admiration, not scrutiny.

It was Stanley’s contribution to the runaway hit soundtrack to the film O Brother, Where Art Thou? that lionized him to a whole new crowd. It turned this squat, rigid man into the mainstream avatar for the American roots-music scene. On stage at New York’s Bottom Line on June 12, he played up that role, opting for a hermetic stage presentation. In the wake of the O Brother phenomenon, he’s now supporting a new homonymous album on Columbia’s DMZ imprint — which is helmed by O Brother music supervisor T-Bone Burnett. On the venue’s small stage, Stanley stood, unassuming and still, in the middle of his performing troupe — not the Clinch Mountain Boys of O Brother but a pared-down touring foursome. The microphones the group used were in the style of the ’30s and ’40s — bulbous, waffled knobs jutting up from a stand. If they weren’t vintage, they were precise re-creations. Not once did Stanley lean in toward his. Instead, he tilted his head slightly upward, aiming each song at some indeterminate spot along the back wall.

Dressed in black with minimal floral embroidery on his shirt, he delivered the set with grim conviction tempered with occasional flashes of levity, as if he were amused by his newly acquired iconic status. From time to time, he’d ’fess to forgetting the title of a tune, though he could as easily have been slyly making light of his advanced age. Just as often, he’d pinpoint his first recording of a particular standard — almost every time, it was 1948, apparently a bountiful year — and then break into a faultless tenor. Stanley doesn’t need a band; his best moments are the unaccompanied ones that lay bare all the cracks and splinters a voice naturally accumulates over six decades of song.

Although there’s little studio polish on his new album, it’s no substitute for the live experience. Even the relatively restrained New York crowd was on a few occasions incited to fever pitch by Stanley and his band. He opened with an unaccompanied version of "Twelve Gates to the City," a song that, in context, sounded almost like a paean to a wounded New York. Both "The Death of John Henry" and "I’ll Remember You Love in My Prayers" were mournful and enthralling in their rendering of the hollow heart. (On the other hand, he omitted one of his trademark O Brother tunes, "O Death.")

Yet despite the visceral quality of the sound, the contemporary bluegrass revival, and Stanley in particular, feels studied in an almost academic way. A genre fixture for the better part of the 20th century, Stanley is something of a relic who’s been treated with kid gloves. He still controls the stage with impressive presence, but people now flock to him for a whiff of the expected, not the unusual.

At the end, he was quickly coaxed back on stage for an encore to deliver a song he’d been holding tight to all night. The crowd burst into applause at the first elongated syllables of the signature O Brother tune "Man of Constant Sorrow," which he introduced by saying that his version, which he’d been singing for 50-odd years, was somewhat different than the one that the film had made so popular. But the changes were at best superficial. Stanley cut to the song’s lamenting core, removing it several steps from the shuffling version that emanates out of George Clooney’s mouth (actually sung by Union Station’s Dan Tyminski) in O Brother.

Finally, he went for the patriotic jugular, albeit subtly. Returning for a second easily solicited encore, he asked the audience to hold hands and then launched into a call-and-response rendition of "Amazing Grace." He’d feed the audience a line in his unique, tattered drawl, which was strewn with unusual accents, then politely listen as it was sung back to him en masse, in a style closer to the song’s more traditional phrasing but taking cues here and there from his distinctive interpretation. Not a single person in the house failed to follow Stanley’s direction. After all, when history itself comes calling, you can’t say no.