Max Kalbeck was a close friend and partisan of Johannes Brahms. Kalbeck's principal achievement was his eight-volume biography of that composer, published from 1904 to 1914, which has never been translated into English. Kalbeck also edited several volumes of Brahms's correspondence and in 1918, the letters of the poets Gottfried Keller and Paul Heyse, as well as publishing two collections of his own music reviews. Kalbeck wrote new libretti for Mozart's "Bastien und Bastienne" and "La finta giardiniera"; and he revised those of "Don Giovanni" and "The Marriage of Figaro" for Gustav Mahler's productions at the Vienna Hofoper. In addition, he supplied
Moses und Aron about the number 13; "Moses und Aaron" has 13 letters. Zoltán Kocsis (Hungarian conductor, composer and pianist) had received permission from Schoenberg's heirs in 2009 to complete the last act. His version was premiered in concert at Budapest on 16 January 2010. As Schoenberg always intended to finish the work, the opera was not performed during his lifetime. However, the first public performance of music from the opera was of "Der Tanz um das goldene Kalb" in concert at Darmstadt on 2 July 1951, just 11 days before the composer's death. There was a concert performance of the two acts