An exploration of 20th Century music arranged by category into three broad groups: concert music, popular music, and world music. In our present era of musical pluralism and technology, styles are exchanged and combined so freely that we owe it to our cultural continuity to look at as many kinds of music as time will permit. Aspects to be discussed are the role of 20th Century music in society, its reception by audiences, its relation to other arts and to political and economic factors, and its theory and pedagogy.