Move over, Monteverdi! Stephanie Fleischmann’s violent, blood-drenched scenario subjects sketchy Roman historiography to an unsparing, necessarily speculative 21st-century feminist critique. The music is by Michael Hersch, who flutters to the darkest of subject matter like a moth to the flame, weaving scores that have the weight of a glacier on granite yet glisten with a darting quicksilver brilliance. —M.G.