The first time I saw Nick Thorburn perform he was wearing a pink tuxedo, and with good reason: although his group, the Unicorns, sang songs about things like death, ghosts and nautical catastrophe, they did so with the youthful exuberance of mischievous teenagers headed to prom. Thorburn and his bandmates took to the stage, then the rafters, then the outstretched hands of an audience full of newly-minted fans. The Unicorns blew up, burned out and…