Mr. Kraber held executive positions in radio and television and was well known as a folk singer, having recorded several albums of American ballads and folk songs.
He is best known for acting, having been seen on and Off Broadway since 1927. He was a founding member of the Group Theater, producing such triumphs of the 1930's as the Pulitzer Prize-winning ''Men in White,'' Saroyan's ''My Heart's in the Highlands'' and Odets's ''Waiting for Lefty.'' In 1952, Elia Kazan, the Broadway and Hollywood director, accused Mr. Kraber of being a Communist at a hearing before the House Committee on Un-American Activities. Mr. Kazan said they had been in the same Communist unit. Mr. Kraber refused to respond to the charge.
Mr. Kraber went on to make films, including the prize-winning documentary ''Boundary Lines.'' In 1977, he appeared as the old man in the New York production ''Nobody Heard the Lions Roar.''
He was married to the former Wilhelmina Barton and had a son, Karl, and two granddaughters.
