The document summarizes elements of 20th century music and characteristics of contemporary music. For elements of 20th century music, it discusses less emphasis on blended sound, percussion playing a major role, and individual tone color being clearly heard. It also discusses the use of polychords, tone clusters, polytonality, and bitonality. For characteristics of contemporary music, it briefly outlines seven categories: impressionism, non-classicism or new baroque, expressionism, nationalism, futurism, computer music, and popular music and jazz. The document provides an overview of key changes in musical elements and genres in the 20th century.