In this all-Mahler program, Iván Fischer and his boldly original Budapest Festival Orchestra are joined by German contralto Gerhild Romberger for the heart-rending Kindertotenlieder, poignant lamentations on the death of a child. The evening concludes with the arresting Symphony No. 5, an enduring monument to the composer’s belief that “a symphony must be like the world; it must embrace everything.”