Anger is rarely expected in bluegrass -- especially not from Nickel Creek, three musicians in their twenties who have been playing together since childhood. Sunday night at the 9:30 club, the trio didn't quite reach all-out wrath, but the evening's most memorable songs were the most aggressive. Chris Thile pounded his mandolin on "Helena," Sara Watkins almost wailed on "Best of Luck," and Sean Watkins's passionate guitar playing captured heartbreak on "Somebody More Like You."

Even on its happier songs, the group maintained intensity: The trio jumped back and forth between the Band's "Up on Cripple Creek" (complete with an exuberant yodel) and a furious version of "The Fox." During long instrumentals, the three musicians moved around, often ending up clustered at center stage, feeding off one another's energy.

Those instrumentals told as much of a story as the songs with lyrics. When Sean Watkins introduced "Stumptown," a tribute to a Portland, Ore., coffee shop, Thile interrupted to tell about his doctor's orders not to consume caffeine. "While the song will remain boisterous," he concluded in mock solemnity, "you'll catch some deep sorrow." Thile did play up his mopiness during the song's bridge, but he quickly leapt out of his funk and bounced around the stage, his stamina reflecting Nickel Creek's highly energetic set.

-- Catherine P. Lewis