Moses und Aron has its roots in Schoenberg's earlier agitprop play, Der biblische Weg (The Biblical Way, 1926–27), a response in dramatic form to the growing anti-Jewish movements in the German-speaking world after 1848 and a deeply personal expression of his own "Jewish identity" crisis. The latter began with a face-to-face encounter with anti-Semitic agitation at Mattsee, near Salzburg, during the summer of 1921, when he was forced to leave the resort because he was a Jew, although he had converted to Protestantism in 1898. It was a traumatic experience to which Schoenberg would frequently refer, and of which a first mention appears in a letter addressed to Wassily Kandinsky (April 1923): "I have at last learnt the lesson that has been forced upon me this year, and I shall never forget it. It is that I am not a German, not a European, indeed perhaps scarcely even a human being (at least, the Europeans prefer the worst of their race to me), but that I am a Jew."
Schoenberg's statement echoed that of Gustav Mahler, a convert to Catholicism, some years earlier: "I am thrice homeless: as a Bohemian among Austrians, as an Austrian among the Germans, and as a Jew throughout the entire world. I am an intruder everywhere, welcome nowhere."
The Mattsee experience was destined to change the course of Schoenberg's life and to influence his musical creativity, leading him first to write Der Biblische Weg, in which the central protagonist Max Aruns (Moses-Aaron) is partially modelled on Theodor Herzl, the founder of modern political Zionism; then to proclaim in Moses und Aron his uncompromising monotheistic creed; and finally, upon his official return to Judaism in 1933, to embark for more than a decade on a relentless mission to save European Jewry from impending doom. Der Biblische Weg should be considered as both a personal and political play. Moses, at the center of the biblical Exodus story, had become from the time of Heinrich Heine to that of Herzl and Schoenberg, the ideal incarnation of a national and spiritual redeemer.
From the sketchy outline of the play (1926) to its final version (1927) and to the inception of Moses und Aron as an oratorio (1928), it then became an opera, and the first two acts were composed between 1930 and 1932. Schoenberg often stated his intention to complete the work but composed only a few sketches for Act 3. Despite its unfinished status, it is widely regarded as Schoenberg's masterpiece.
Schoenberg's title may have omitted an "A" in Aaron's name because the composer was severely superstitious 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.