The notion of going to a "Gillian Welch show" is somewhat misguided, in that it's likely the singer/songwriter has never played as many as one live date without the presence of longtime musical partner (and guitarist/vocal harmonist extraordinaire) David Rawlings by her side. The two strode onstage Portland's cult-famous Aladdin Theatre without so much as an introduction or opening act, with Welch resplendent in the red floral dress that graces the cover of her latest release - the instant classic Time (The Revelator) - and Rawlings in his typical mortician's get-up (black suit, white shirt, little else in the way of adornment). To say the two spent the next three hours blowing back the hair of all present is to understate the truth of this amazing evening.

Despite the three-year gap between Time and its predecessor, the understated and terrific Hell Among The Yearlings, Welch and Rawlings have been plenty busy. The duo provided instrumental and vocal backing for ex-Whiskeytown frontman Ryan Adams' first solo album, Heartbreaker, and contributed in major fashion to the record that essentially broke "No Depression" with the masses: the soundtrack for the Coen brothers' Depression-era fable O Brother, Where Art Thou? (Welch has a brief cameo in the film). The success of the latter has certainly had the effect of burnishing Welch's already bright star; tonight's show was sold out weeks in advance, and those in attendance sat with the kind of rapt attention typically associated with Austin City Limits or other public-television fare (none of which, in any event, seemed to faze Welch in the least).

The duo's first set was largely dominated by material from Time, with Welch trading off between guitar (the Appalachian lullaby "Dear Someone," the Everlys-like "I Want To Sing That Rock And Roll") and banjo (the poignant "My First Lover," which contains a cheeky quote from the old Steve Miller tune "Quicksilver Girl") while Rawlings blazed away with an almost free-form guitar accompaniment that ranged from inspired rhythm counterpoints to solos that shot sparks into the air (his loose-limbed fretboard work on "Red Clay Halo" literally brought down the house). The two make for a compelling duo; plying a stark and gloriously moody update of antique American music forms, there's an intelligence that marks their work without rendering it sterile or academic, calling to mind legendary forebears such as the Carter Family, Stanley Brothers and Louvins without necessarily copping their styles outright. When the pair adds its own modern sensibility to this folk-informed template (such as on this evening's cover of the Townes Van Zandt tune "I'll Be Here In The Morning"), the results can be electrifying.

After closing the first set with the Revival-era favorite "By The Mark," Welch and Rawlings kicked off the second set in style by providing some background on the title track of their recent release. "David, do you remember the first time we ever played this song?" Welch asked her partner. "It was here, in Portland, the last time we came through. We finished it up in the hotel room; and I can tell you from the reception you all gave it that night, we left here a little shaky." "Revelator" is absolutely the best of what Welch has to offer the world: a melody and storyline to kill for, delivered in her matter-of-fact stoic's voice, pitting beauty against dread in a way that favorably compares her work to that of Robert Johnson, Leadbelly or Billie Holiday - blues from way down deep in the soul. She is as convincing and committed a singer as there is working today, and this evening's performance of her true "killer app" reminded me yet again of why Welch can stand proudly among such legendary company.

As ever, the encores are where Welch and Rawlings allow their craft to go slightly off the rails, and on an evening that saw the pair return to the stage four times, there were ample opportunities to convey their core themes of death, prayer, regret and remorse. Tonight, two particular numbers stood out: a playful, unplugged run-through of the obscure bluegrass artist John Hartford's "Nobody Knows What You Do" (sung from the foot of the stage to the balcony audience) and a somber reading of Neil Young's Tonight's The Night epic "Albuquerque." As the two made their way through the narrative twists in the song, their heads bowed and eyes closed in an almost Pentecostal reverie, they communicated in much the same way as twins, silently urging each other on through the feel and intuition acquired with a lifetime's worth of personal knowledge. A humbling and inspired set from two masters of what Gram Parsons once called "Cosmic American Music."