Bob Wilcox and Gerry Kowarsky review (1) THE GERSHWINS’ PORGY AND BESS, by George & Ira Gershwin, DuBose & Dorothy Heyward, and Suzan-Lori Parks, at The Muny, and (2) TARZAN, by Phil Collins and David Henry Hwang, at The Muny. Then Bob and Gerry interview Zulimar Lopez Hernandez (soprano) and Tim Ocel (director) of Union Avenue Opera’s upcoming production of Verdi’s “La Traviata.”