Merce Cunningham died in 2009 at the age of 90, and in his decades-long career as a dancer and choreographer, he redefined American modern dance as we know it. Fond of reminding his dancers, audiences and the media that he wasn’t designing the movements but rather allowing them to be revealed, Cunningham broke the mold of what the performing arts understood dance to be, from the way his work unfolded to the way he ran his eponymous dance company. Alla Kovgan’s captivating new documentary—fittingly titled Cunningham—explores the artist’s work, life and lasting legacy in a film that blends the past and the present in beautifully inventive ways. In order to…