When director David Almaral and composer Joshua Dumas started adapting Raymond Carver’s short story “Gazebo” for the stage, they envisioned acting, singing, narration, and an evening-length score. But how to classify the thing they were cobbling together? It wasn’t a musical, really, or an opera: only one character would sing, and her songs would be limited to brief, internal monologues. Then they stumbled on an article about semi-opera, a Restoration-era form that combines dramatic scenes with masquelike musical pageants. Close enough for a press release. “It was just so people wouldn’t think they were coming to an opera,” Almaral admits. In truth their delicate, sophisticated show, One Thing, and Everything Else, which closed in May at Building Stage, was something entirely new: a mash-up of semi-opera and chamber theater, with a pinch of 60s-era theatrical ritual. They plan to keep developing the form. Maybe they’ll even figure out what to call it.