Valda Setterfield has been a groundbreaker and a muse for more than half a century, notably as an early member of Merce Cunningham's company. Now the Irish choreographer John Scott has tapped Ms. Setterfield to portray Shakespeare's mad monarch in their collaborative production, "Lear." Created in response to his father's death, Mr. Scott has called the work "a meditation on loss of memory and physical failings." To continue the gender flip, King Lear's children are portrayed by men.