Nickel Creek is still pickin’, but it’s no longer grinnin’. A stark departure from its earlier upbeat efforts, the group’s recent Why Should the Fire Die? compiles bleak folk parables, brokenhearted ballads, and poignant Elliott Smith-style pop. The trio still harmonizes frequently and flawlessly, but each of the group’s singer-songwriters gets at least one solo showcase. Intertwined mandolin, fiddle and guitar play mystical-sounding melodies over death-march percussion, as singer Chris Thile asks, Where can a sick man go/When he can’t choke down the medicine?. On Sean Watkins’ bitterly tormented “Someone More Like You,” he delivers a string of barbed well-wishes: I hope you meet someone your height/So you can see eye to eye/With someone as small as you. Sara Watkins masterfully interprets Bob Dylan’s “Tomorrow Is a Long Time” and vocally recalls Dolly Parton on a crackling vintage-country track. Nickel Creek ambitiously reaches past bluegrass’s borders without compromising the genre’s integrity, meaning it can expand its fanbase without sacrificing its core audience.