Mezzo-soprano Hanna Schwarz, born on August 15, 1943, has had a successful career that hasn’t always seen her in the limelight.  She studied psychology and voice in Hamburg, before becoming a member of the Staatsoper Hannover.  In a career marked by her interpretations of Wagner, it is surprising to see her first major success come as Maddalena in “Rigoletto.” But {…}