At 7:30 tonight and at 8 tomorrow night at Mandel Concert Hall, the Cleveland Orchestra delivers a special program curated by conductor Franz Welser-Möst. The evening kicks off with Poulenc’s La voix humaine, a monodrama starring French soprano Sarah Aristidou. It concludes with Richard Strauss’s Symphonic Fantasy on Die Frau ohne Schatten, an opera he considered his “most important work.”