The genesis of Arnold Schönberg’s theoretical writings of the American period lay in the pedagogical work that Schönberg found it necessary to provide for his students who lacked sufficient background for advanced study in theory and composition. Structural Functions of Harmony stand in direct succession to the Harmonielehre (Theory of Harmony). The concept of region, as an enlargement of modulation was introduced in earlier writings, than in Structural Functions, where it is considered as being derived from the principle of monotonality.