Almost any three-dimensional shape can stand in as sculpture—or at least prompt us to ask, What is sculpture? Between the 1960s and 70s, answers to that question went beyond traditional dimensions. Sculptors began playing with video installations, lighted space, and—incredibly—sound-only works. Fifty years later, sound as sculpture continues to test the boundaries of convention. In this exhibition, foundational works from that decade are paired with contemporary explorations. —E.C.