Viktor Ullmann, a Czech student of Arnold Schoenberg, did not stop composing, even when he was headed for the gas chambers.Imprisoned at Terezin in his home country, Ullmann threw himself into his work, turning out opera, theater music and vocal and instrumental work before he was deported to Auschwitz on Oct. 16, 1944. He probably died in the gas chambers the next day.His work survived. His music, set to the lyrics of Rainer Maria Rilke, will be performed Tuesday at “Testaments of the Heart,” an unusual concert of music from various artists, all composed in concentration camps. The concert will be at Emory University’s Schwartz Center for the Performing Arts.The music has been feverishly collected over the past 20 years by Italian pianist and conductor Francesco Lotoro, who will be performing several of the works, along with musicians from the Atlanta Symphony Orchestra, the Georgia State University Orchestra and Emory’s Department of Music.Part of Lotoro’s intensity is a conviction that many of these scores are disappearing, through loss, neglect or just the ravages of time.