Cosi fan tutte By Wolfgang Amadeus Mozart, liberetto by Lorenzo da Ponte Performed by the Boston Youth Symphony Musical Direction by Federico Cortese Performed in Italian, with subtitles Sunday, 3 p.m. Sanders Theatre, Harvard University Ticket information On Sunday, the 119 members of the Boston Youth Symphony, joined by a cast of operatic talent, will perform a semi-staged production of Mozart's Cosi fan tutte, a comedic work that tackles the question of fidelity among lovers......