For the second time, Elena Bashkirova, pianist and president of Leipzig’s Felix-Mendelssohn-Bartholdy-Stiftung, has invited a group of musician friends to gather for a two-day Mendelssohn Festival at the Pierre Boulez Saal—located just a few blocks from the composer’s historic Berlin home. In addition to works by Felix and his sister Fanny, the program includes music by Hans Krása, Viktor Ullmann, and Gideon Klein, three 20th-century Jewish composers persecuted and murdered during the Nazi era.