In the summer of 1944 a delegation of Nazi officials, including Adolf Eichmann, hosted representatives from the International Red Cross at Terezin concentration camp. The visit had been meticulously planned: gardens planted, barracks renovated, streets cleared. Thousands of prisoners were deported eastward to reduce overcrowding. The elaborately staged tour, held on June 23, culminated with a performance by Terezin’s inmate choir. Conductor Rafael Schächter chose to perform Giuseppe Verdi’s “Requiem.”

“When the music stopped, the Nazis sat there in silence,” recalls Zdenka Fantlova, 96, a survivor of Terezin. “Then Eichmann murmured, ‘Interesting, very interesting.’ ” Following his cue, nervous applause trickled through the hall. Ms. Fantlova adds, “The Nazis thought, why would Jews perform a Christian prayer for the dead? But Schächter had his reasons.”

Verdi’s nearly 90-minute masterpiece features a fearsome evocation of fire and fury, promises of posthumous punishment, and dire warnings of God’s wrath. While other settings of the Latin text omit the unsettling sequences and emphasize only eternal rest and serenity, Verdi accentuates the themes of judgment, justice and vengeance. The apocalyptic hymn “Dies Irae” is repeated throughout. “Therefore when the Judge takes his seat, whatever is hidden will be revealed: Nothing shall remain unavenged.”

“Rafael said we would sing to the Nazis what we couldn’t say to them,” says Marianka May, 95, a Terezin survivor who sang in Schächter’s choir. “The Latin words remind them that there is a judge, and one day they will answer to that judge.”

Terezin was a ghetto and transit camp in German-occupied Czechoslovakia. It usually housed around 60,000 inmates, most of whom would in time be deported to extermination camps such as Treblinka and Auschwitz. Terezin became a hub for the Jewish intellectual elite—titans in politics, music and academia. A vibrant cultural scene flourished amid the desperation, with lectures, concerts and plays performed within the barracks.