The Canadian band Moxy Früvous captures, with beautiful acuity, that part of the heart that teeters between adolescent romanticism and adult cynicism. Its attitudes, lyrics, and melodies ask "why?," while carrying the answer that humans are mortal, things break, and life is imperfect.The guys in Moxy Früvous would probably snort (harmoniously) upon reading that sentence, for, despite the sharp moralism of their songs, they don't take themselves too seriously. The Früvous attitude is epitomized in "King of Spain," the rollicking tale of an ex-monarch who maintains his pride despite his new rank as pizza cook. It's about laughing all the way to the undertaker.A small but enthusiastic crowd welcomed the group to the Birchmere. Most seemed to be longtime Früvians; when asked to join in on the chilling anti-war ballad "The Drinking Song" (a.k.a. "And the band played on..."), the crowd chimed in on some of the verses as well as the chorus.Opening the show was Da Vinci's Notebook, an a cappella quartet from Arlington, Virginia. The group's clever covers ("Is She Really Going Out With Him?," "Pinball Wizard") and originals are balanced by tight, appealing harmonies and a winning stage presence. The barbershop arrangement of rock songs, appropriately titled "Metal Shop," drew a more enthusiastic crowd response than some headline acts enjoy.