Czech composer Hans Krasa wrote the children's opera Brundibar in 1938 for a Jewish orphanage in Prague, but it didn't have its premiere until 1943, in an attic theater at Theresienstadt--a concentration camp north of the city where inmates were encouraged to pursue the arts, and which the Nazis used as a showcase to placate international observers. (An excerpt from a filmed performance of the piece was included in a German newsreel as evidence of the camp's success.) During his internment Krasa added a dark, complex overture that opens the opera on a troubled note, but its basic story is sweet and simple: a brother and sister, too poor to buy milk for their sick mother, sing for money in the streets; when an organ-grinder named Brundibar grows jealous of their popularity and tries to bully them, they band together with other children and a group of animals. The opera was performed for the camp's children, with young inmates in the lead roles, more than 50 times before Krasa was shipped to Auschwitz, where he died in 1944. Though his early work was reputedly influenced by Ravel, Stravinsky, and early Schoenberg, the chief reference point for Brundibar, his only significant surviving composition, is Kurt Weill: most of the tunes are jazzy, piquant, and rhythmically a bit askew. The music can be sung fluently by children, and since the whole piece is only about 40 minutes long they don't find it too taxing; restless young audiences appreciate the score's playful leaps between marches, polkas, and waltzes. Chicago Children's Museum cofounder Annette Faber has known about Brundibar for a long time, but after she heard a recording of it during a visit to Prague three years ago she persuaded the Chicago Children's Choir, the Chicago Youth Symphony Orchestra, and Lookingglass Theatre Company to mount an English-language version here. The production, designed by director David Kersnar of Lookingglass, will begin with a scene-setting narration that describes the Nazi occupation and Theresienstadt against a backdrop of period newsreels and slides of camp children's drawings; cantors Alberto Mizrahi and Deborah Bard will then offer songs of blessing. At the opera's conclusion original cast member Ela Weissberger will join the young ensemble for a reprise of the final triumphant chorus, sung in Czech. Saturday, 8 PM, and Sunday, 1 and 4 PM, Merle Reskin Theatre, 60 E. Balbo; 773-871-3494.