The grace and coherence that mark Laura Veirs's fourth album, Carbon Glacier (Nonesuch), were hard-won: it took five years and two flawed albums for the Seattle singer-songwriter to fulfill her early promise. On last year's Troubled by the Fire Veirs's lyrics began to shift from trite to sharply observed, and her music underwent similar improvements. That album's adventurous sonic aesthetic, thanks to producer Tucker Martine and the atmospheric contributions of guitarist Bill Frisell, helped Veirs move well past her folk and country roots. Carbon Glacier builds on Troubled's template. A song cycle rich with winter imagery, Glacier takes inspiration from Veirs's childhood in Colorado: "The sky's a raven marching band black blizzard blowing across the land," goes one typical line. Her songs tackle the big issues of singer-songwriterdom--death, displacement, isolation, loneliness--but now that she's matured beyond the predictable agit-folk of her early career, she's capable of sidestepping most of the attendant cliches. Nora O'Connor headlines; Winter Blanket opens. Friday 22, 10 PM, Schubas, 3159 N. Southport, 773-525-2508, $8 in advance, $10 at the door.