Karas spent more than 50 years teaching violin at the University of Hartford's Hartt School of Music and performing with the Hartford Symphony.
His second career of discovering lost music began in the summer of 1970 after reading an article in a Czech music magazine about the recovery of fragmentary musical works composed in Theresienstadt, which also was known as Terezin after the Czechoslovak town in which it was located.
Karas spent the next decade pursuing and uncovering "extensive musical activities and even creativity in, of all places, a Jewish concentration camp," he wrote in his 1985 book "Music in Terezin, 1941-1945."
In all, Karas discovered more than 50 compositions written at Theresienstadt.
"Why should I, a Christian, get involved in a research project virtually untouched for 25 years, since the last puff of smoke had darkened the skies of Auschwitz?" he wrote in his book. "I felt attracted to the project because I am a Czech musician, and this was a subject dealing with the music of Czechoslovak Jews."
During the years described in the book, more than 140,000 Jews passed through Terezin. An estimated 33,000 died there and 90,000 were sent to other camps, including Auschwitz.
The camp had at various times a high number of Jewish composers among its population. Musical instruments were forbidden at first, but Jews smuggled them in, and musical performance and composition were soon encouraged by the Germans because of the propaganda value gained during visits by the International Red Cross and other observers.
At least 15 men composed music at Terezin. One of the most prolific, Viktor Ullman, who had studied with Arnold Schoenberg, wrote in his journal: "Theresienstadt has not hampered my musical activity, but has actually encouraged and supported it. In no way have we merely sat lamenting by the rivers of Babylon; our cultural will has been adequately proportional to our will to live."
The children's opera "Brundibar" by composer and inmate Hans Krasa was performed more than 50 times in the camp, once during a much-recounted visit by the Red Cross.
In preparation for the arrival of Red Cross officials, the Nazis cleaned up the camp by repainting the buildings and deporting the old and infirm to Auschwitz. The opera's cast frequently changed as the child performers were sent to Auschwitz. Krasa was sent to the gas chamber a few months after the Red Cross performance.
The opera was featured in a propaganda documentary commissioned by the Nazis and whose Jewish director was sent to Auschwitz shortly after he completed it.
Karas received the score of "Brundibar" on a visit to Prague in 1970, and he conducted its American premiere in West Hartford in 1975.
He and his wife, Milada Javora Karas, translated the opera, but she died in 1974, before the English libretto could be performed. "Brundibar" was first performed in English in 1977 in Ottawa and recently was revived in a new translation by Pulitzer Prize-winning playwright Tony Kushner.
Josef Marie Karas was born May 3, 1926, to a Christian Czech family in Warsaw. His father, a Czech government official, was active in the underground resistance during World War II, gathering information and assisting Jews.
Karas fled Czechoslovakia in 1949 after the Russian occupation; his father was executed not long afterward. The younger Karas passed through a series of refugee camps before settling in the United States.
He studied violin at the Prague Conservatory and joined the Hartford Symphony and the faculty at the Hartt School of Music in 1955. He played with the symphony until retiring in 2006.
Survivors include his wife of 33 years, Anne Killackey Karas; six children from his first marriage; two brothers; a sister; and seven grandchildren.
Remington writes for the Washington Post.