If Robert Fripp had discovered mandolin and bluegrass instead of guitar and classical symphonies, he might have formed a band like The Punch Brothers instead of King Crimson. The honor of actually founding the Punch Brothers goes to former Nickel Creek mandolin player Chris Thile. The MacArthur Fellow kick-started the progressive bluegrass quintet in 2006, after his old band's dissolution, and immediately put the "prog" to work. In 2007, Thile performed a four-movement, 40-minute suite at Carnegie Hall titled "The Blind Leading the Blind," reportedly inspired by his 2003 divorce. It would comprise the majority of the Punch Brother's self-titled 2008 debut. Their subsequent 2010 release, Antifogmatic, continued to build on that template pushing the rootsy, new-grass spirit beyond the mountains and Celtic inspirations. The jazzy, dramatic arrangements are characterized by changing dynamics, tempos, and time signatures, but they're delivered with such a seasoned, understated touch that they're little more than tight corners in an invigorating ride. Thile keenly balances his arty impulses with hooks, craftsmanship, and flair. Many of the songs on last year's third LP, Who's Feeling Young Now, move with a woozy rag-tinged amble reminiscent of the Squirrel Nut Zippers. The blend of "hillbilly" music and jazzy NPR sophistication gives lie to old classist genre divisions.