The document discusses trends in 20th century music and categorizes composers into groups based on their stylistic approaches. It outlines categories including Traditional/Conservative composers who worked in established forms, Progressive composers who explored new techniques as extensions of traditional styles, and Avant-Garde musicians who reconsidered the nature of music. Specific composers are given from Europe and America as examples within categories like Serialism, Neo-Classicism, Experimentalism, Fluxus, and Minimalism. The document also notes additional trends that emerged in the 1970s including Post-Minimalism and Neo-Romanticism.