Apr 10, 2018 Julia Bullock mixed the blues of Bessie Smith, Billie Holiday and Nina Simone into her program at Spivey Hall. (Photo by Dario Acosta) Soprano Julia Bullock has a dilemma. Opera is all about stereotypes a.k.a. fach — role classification based upon a classical singer’s vocal and sometimes physical attributes. (i.e. Does she look more like a strapping Brünnhilde or a dainty nymph?) Bullock’s light, yet earthy sound, prettiness and petite stature place her squarely in the middle of a group of singers the likes of Dawn Upshaw, Barbara Bonney, and Kathleen Battle. She’s a shoe-in for operatic roles like Pamina (Mozart)…