“Rooooowwwwwwrrrraaaarrrrrrrrrooowwwwrrrrrrrr!” A guttural growl straight from the deepest pits of hell has just emanated from the throat of Melissa Cross, who follows it up with a giggle. “See, that didn’t hurt at all. But you should see the looks I just got!” That’s because the chipper, red-tressed, late-fortysomething voice instructor…