Mandolin player extraordinaire and former Nickel Creek member Chris Thile has a new outfit, Punch Brothers, and their debut release is a complex and impressive first outing. Right off, on “Punch Bowl,” things take a turn when a whiff of dissonance permeates the middle part of the track. You are suddenly aware that things are not what they seem, and you know by track’s end this won’t be your granddad’s bluegrass. The songs are rooted in the sorrow of Thile’s own personal pain of a marriage in crisis, and at the heart is an emotional, expansive four-part suite, “The Blind Leaving the Blind,” which demands the most active listening. With shifting time signatures, odd tunings and harmonies, occasional discord, and even jazzy interludes, these pieces are an avant-bluegrass opera, unraveling the narrative both in words and in astonishing musical textures. Of course, there are also simpler moments of musical pleasure, such as the fragile and hopeful “It’ll Happen,” with violin, banjo and mandolin executing a beautifully choreographed pas de trois with all the grace those instruments are capable of.