“‘Don’t look at the mirror, look at your feet,’ Michelle Dorrance corrects. Smiling at the counterintuitive suggestion, Gillian Murphy, Devon Teuscher and Christine Shevchenko — American Ballet Theatre principals accustomed to projecting up and out to opera house balconies — look down at their pointe shoes as they shuffle into a line of tight fifth positions. As polyrhythmic strains of music fill ABT’s studios, the trio flashes through small, quicksilver position changes while Teuscher quietly counts a steady 4/4 beat that isn’t yet audible in the music.”