The Valley of Astonishment, Polonsky Shakespeare Center, New York

This calm, fascinating, rather chilly 75-minute theatre piece, written and directed by Peter Brook and Marie-Hélène Estienne, grew out of an earlier work, Je suis un phénomène, devoted to memory. This time, the subject is primarily synaesthesia, the condition that makes people involuntarily associate something with an unexpected sense. The word blue “tastes” inky, or a D-sharp “looks” mauve. I first encountered synaesthesia in the writings of Vladimir Nabokov – he, his wife and their son had the condition – but the authorial presence for Brook and Estienne is Oliver Sacks, as it was for Phénomène and The Man Who. If, for humans, the brain is the final frontier, these three explorations provide a fitting, near-final summa for the career of Brook, who is 89.