On a cold October night in 1942, SS guards at Sachsenhausen violently disbanded a rehearsal of a secret Jewish choir led by conductor Rosebery d'Arguto. Only one of its members survived the Holocaust. Yet their story survives, thanks to Aleksander Kulisiewicz. An amateur musician, he was not Jewish but struck up an unlikely friendship with d'Arguto in Sachsenhausen. D'Arguto tasked him with a mission: to save the musical heritage of the victims of the Nazi camps.

In Sing, Memory</...