This year Ravinia’s annual Gala Benefit Evening, sponsored by the Women’s Board in the year of their 50th anniversary, fittingly showcases two knockout women singers, both of them Ravinia favorites: soprano Patricia Racette, who has won accolades here in the title roles of Madama Butterfly and Tosca, and Broadway icon Patti LuPone, whose Ravinia credits have included star turns in Gypsy, Annie Get Your Gun and a string of Stephen Sondheim-composed musicals. These two unique artists, together and separately, will musically demonstrate the power of the feminine mystique.