The post-Balanchine choreographer William Forsythe has inspired so many poor imitations that until you see the originals, you may wonder why. Why? Because the restless 73-year-old American is always advancing, revising, enhancing. Because he takes up where Balanchine—in his syntax, his impulse toward bigger, faster, and more off-balance—left off. Because he’s punk, poking holes in the fourth wall. Because he’s got range, from a heedless emotionality that catches a person by surprise to a cerebral rigor as slippery and unforgiving as ice. The Nederlands Dans Theater lays this all out in a Forsythe triple bill that includes a stealthily heart-catching duet from 1995 and a couple of his seemingly messy, secretly carefully calibrated ensemble pieces, including one made recently, for the stellar company’s current members. —Apollinaire Scherr