“Sad bastard music” has been a stubbornly resilient descriptor of Belle & Sebastian‘s music, a band who, fifteen years ago, helped popularize a phrase that launched a thousand self-conscious dorm-room wallflowers. But a lot has changed since then. “The only thing worse than being miserable is sentimentalizing misery as a desired state,” said lead singer Stuart Murdoch in a recent The New York Times Magazine profile. If Murdoch once took satisfaction in the gloomy recesses of youth, his band has gradually shed its melancholic worldview for a more satisfying and, as last night’s performance at D.A.R. Constitution Hall proved, wickedly-entertaining identity.