20th century music (1901–2000) includes the modern period (1890-1930) that overlaps from the late 19th-century, the high modern (mid 20th-century), and contemporary (1975–2000) period, the last of which overlaps into the 21st-century. Diversity is the main feature of 20th century music, as much was reactionary to previous musical developments and composers explored musical composition in quite different ways.

At the turn of the century, music was characteristically late Romantic in style. Composers such as Gustav Mahler, Richard Strauss and Jean Sibelius were pushing the bounds of Post-Romantic Symphonic writing. At the same time, the Impressionist movement, spearheaded by Claude Debussy, was being developed in France. Maurice Ravel's music, also often labelled impressionist, explores music in many styles not always related to it.

Many composers reacted to the Post-Romantic and Impressionist styles and moved in quite different directions. The single most important moment in defining the course of music throughout the century was the widespread break with traditional tonality, effected in diverse ways by different composers in the first decade of the century. From this sprang an unprecedented "linguistic plurality" of styles, techniques, and expression. 20th Century Music included several movements, including: "Impressionism," "Modernism," "Futurism,""Free dissonance and experimentalism," "Post-modernism," "Expressionism," and "Minimalism."

"Atonality and twelve-tone technique" The 20th century also saw the rise of jazz & electonic music. Edward Elgar George Enescu Gabriel Fauré Morton Feldman Alberto Ginastera Henryk Górecki Alan Hovhaness György Ligeti Witold Lutoslawski Bruno Maderna Bohuslav Martinu Carl Nielsen Harry Partch Krzysztof Penderecki Francis Poulenc Giacomo Puccini Sergei Rachmaninoff Alfred Schnittke Michael Tippett Ralph Vaughan Williams Heitor Villa-Lobos William Walton Steve Reich Arnold Schoenberg