Abigail Washburn at the Tin Angel

This review would be simple if Abigail Washburn were simply a "Banjo Pickin' Girl." That's a song from her second album, a traditional tune played by vintage string bands as part of folk music's rich tapestry.

But Washburn, an Illinois-born clawhammer-style banjoist and singer, had to go and complicate things, touring Tibet and writing melodies and lyrics with a diversity of inspirations: old-time country, British folk, American gospel, Kazakh music. She even writes tunes in Chinese.

While these intriguing nuances filtered through every moment of her Tin Angel showcase on Wednesday, what was most amazing was her pairing with pop songwriter/multi-instrumentalist Kai Welch. It's the center of her new album City of Refuge.

As Washburn said at the outset, it was a night of old Appalachian folk meets indie pop. She sure didn't mean conventional indie pop. At times, the five-piece band's softly spare and humming vibe veered toward hootenanny, as in its bracing take on the folk standard "Nobody's Fault but Mine." In the grooving "Shotgun Blues," Washburn did what she called a "switch" on the usual murder ballad - that is, in this one, the woman's hunting the man. Washburn's shimmering, achy vocals and repetitive plucking grew in ire throughout "Shotgun Blues" as she belted out lyrics in which the lady had the upper hand.

Throughout two sets, her new album and its wide-ranging, often abstract sound set the tone. Malleted drums and a gently sawed violin were part of "City of Refuge," which moved from folksy ballad to open drone. The intensity of violinist Rayna Gellert grew on the cosmopolitan country cool of "Last Train," while Washburn and Welch harmonized softly until they drifted into the abyss. Welch, who played keyboards, guitar, and a nicely muted trumpet, has the voice of a teenage Neil Young, mildly high and squeaking. But Washburn was a vocal marvel (think a less showy Tori Amos) whose every crack and cry came through loud and clear. The poetic "Dreams of Nectar" and "Burn Thru" were the ensemble's finest moments, rooted in the traditions of bare-boned blues and verdant folk only to drift into bell-toned loops and drones, where space - and not the Appalachian mountains - was the place.