Reasons Why’s release accompanies the pop bluegrass trio’s announcement that it is going on “hiatus,” which many have taken as a euphemism for splitting up. Whatever the case, the greatest hits collection captures their strengths and weaknesses well. The songs are reliably pretty and immaculately sung and performed. It’s easy to hear why bluegrass fans felt betrayed by Nickel Creek because their youth and musical accessibility marked them as the best hope since Alison Krause for bluegrass to reach a mainstream audience.

 

But despite all their loveliness, the songs have a Californian light rock quality to them, and that’s hard to get around, and the lightness is emphasized by the lack of low notes in the band’s acoustic guitar/fiddle/mandolin sound. The best of Californian rock from the 1970s had some gravity, whether it was the Eagles’ fight against the seductive undertow of debauchery, Warren Zevon’s struggle with his demons or Fleetwood Mac’s soap operatic romantic entanglements. Without the dark undercurrent, Nickel Creek is often the musical equivalent of pretty flowers.

 

Nickel Creek’s Chris Thile got a solo album out ahead of Reasons Why, and it sure sounds like the product of someone eager to demonstrate that his mandolin doesn’t automatically mark him as a purveyor of antique music. In addition to Gillian Welch and Jimmie Rodgers covers, he sings the Strokes’ “Heart In a Cage” and the White Stripes’ “Dead Leaves and the Dirty Ground,” and none of the parties are the worse for the effort. The genre-crossing never sounds awkward or forced, and the feel of the album is that it’s the product of someone who grew up liking rock ’n’ roll as much as bluegrass and who figured out how to merge his interests. He doesn’t sacrifice the bluegrass, either; his mandolin is at the center of almost everything, but only showily so on “Watch ’at Breakdown,” and breakdowns are supposed to be showy.