First, enjoy Trouble in Tahiti, a Leonard Bernstein opera about a struggling marriage, which may have reflected his parents' troubled union or foreshadowed his own matrimonial future. It's one of his most down to earth works, but also one your mother is least likely to have heard of. After Bernstein, the Portland Opera goes to musical theater's early days for two 17th- century one-acts, Monteverdi's Il Ballo Delle Ingrate (The Dance of the Ungrateful Women) and Il Combattimento Di Tancredi E Clordinda) (The Battle of Tancredi & Clorinda). We're sensing a theme here. It's Love & Marriage season (for better or worse) at the Portland Opera.