“Wily, omnivorous bluegrass titans” (Village Voice), the Punch Brothers blaze while Grammy-winning mandolin genius Chris Thile, formerly of Nickel Creek, leads gospel and high-lonesome harmonies. They play Carnegie Hall in October. At Duke the tight-knit, countrified virtuosos play “The Blind Leaving the Blind,” a four-movement suite for bluegrass quintet that’s “as nakedly ambitious as popular music gets” (Slant Magazine).