Yvonne Rainer’s Trio A has been performed as an actual trio, a solo, and a pack that moved across the stage like a wave. The choreographer-cum-filmmaker’s radical experiment has been done naked but for the bibs around the dancers’ necks fashioned from American flags, and in fragments filmed at one-sixtieth the speed, with a different dancer for each bit. At the Tate Modern, Trio A will match the Turbine Hall’s massive dimensions (500 feet long, 115 high) with duration: the 4.5-minute solo will repeat for seven hours. In the widely seen black-and-white film of Rainer dancing the piece, the film loops once, to last twice as long as the dance. But the movement is so non-descript that most people don’t notice. Rainer made it that way. She gives each unrecognizable, unrepeated move equal weight and pace, as if it meant no more or less than any other. The effect—particularly when there is a large group, as at the Tate—is otherworldly. Dance as daze. The mind as a muscle releasing its grip. —Apollinaire Scherr