How do simple things get complicated? How do they stay simple once they are complicated? These might, perhaps, be the questions from which choreographer Anne Teresa de Keersmaeker, starts. But in fact, she starts, as all great choreographers do, with the music. “Music is always my first partner,” she once said. And in Fase: Four Movements to the Music of Steve Reich, three linked duets and one solo, there are indeed three people on stage: de Keersmaeker herself, the wonderful Tale Dolven, and Steve Reich, absent but ever present.