This document provides an overview of 20th century music styles including Impressionism, Expressionism, Primitivism, Neo-Classicism, Avant-Garde music, and Modern Nationalism. It lists influential composers from each era such as Debussy, Ravel, Schoenberg, and Stravinsky. Impressionist works focused on mood and atmosphere using extended chords while Expressionist works conveyed strong emotions through atonality. The document also presents assignments on electronic music and asks students to identify composers and their works from different time periods in 20th century music.