Chris Talley Armstrong may look like a hippie librarian with a banjo, but she's got native Southern Illinois twang in her soul. Her trio, now a quartet including veteran guitarists Zane Prosser and Bill Barttelbort, features some of the St. Louis area's sharpest pickers assailing bluegrass standards like they own the copyrights. They don't reinvent or deconstruct the old tunes. They play them with an unbearable tightness of beingbeing pure bluegrass, that is. Bassist Carla Steinkoetter cut her teeth with Alison Krauss, Barttelbort plays fast and fine enough to have earned his stripes as an Illinois flat-picking champ, and Prosser adds cowpoke harmony and the occasional mandolin. As the jamgrass trend threatens to muddy the old-time waters, Talley and friends offer a sweet and clarifying tonic.