In a way, this restored the balance and clarity characteristic of the Classical period. But since composers in the 20th-century period had a different focus, melodic importance was often ignored.

Rhythm deviated from the typical, accepted meter of past periods. Metric time became less regular and, later in the modern era, composers wrote music without any defined pulse at all. In many genres, music had a meter that was abruptly changing. Stravinsky and Bartók incorporated driving rhythms into their music, and jazz pieces made use of syncopation. Using nonwestern rhythm, composers received musical ideas from Africa, Asia, and eastern Europe. But they also featured the songs and dances of Western culture from southeastern Europe, Asiatic Russia, and the Near East (Machlis 129). Examples of these influences are seen in Bartók’s Allegro Barbaro and Stravinsky’s Rite of Spring. Odd-numbered rhythms of five, seven, eleven, and thirteen could change and alternate throughout a composition.

German composer Paul Hindemith spoke of tonality as "a natural force, like gravity" (qtd. in Machlis 23). Expanding tonality in the 20th century to include all twelve tones in a scale with a special focus on a central note, Schoenberg invented a method Austrian composer and conductor Anton Webern (1883-1945) later called serialism in order to change the conventional major/minor tonal system. A certain arrangement of all twelve tones called a tone row serves as the base for a piece, and the composer is allowed to create many versions of the row. Serialism gave composers more musical control, and later expanded from notes to include rhythm, dynamics, and the space between notes (called intervals).

While tone rows provided a strict form of musical organization, some music wasn’t ordered in any specific way at all, but was left to the decision of the performer. Composers also returned to use of modes from the Middle Ages and Renaissance periods. Schoenberg, however, emphatically stated that "there is still much good music to be written in C Major" (qtd. in Machlis 29).

Instead of the typical harmonic chords containing three or four notes, modern composers wrote polychords of five, six, and even seven notes. In addition, polyharmony combined the new and different kinds of harmony available. Polytonality was associated with Igor Stravinsky and his ballet Petrushka, and a listener could hear two different keys sounding at once. Instead of two keys, Schoenberg introduced atonality with no definite key; all notes were the same in importance and emphasis. In most cases, harmony stayed within the defined tonal scale. One modern example is called pandiatonicism, which consists of playing all the white notes on the keyboard.

With new ideas about form, musicians considered "the overall organization of these elements in musical time and space" (Machlis 47). Bringing back Classical period form, pieces typically had the traditional feelings of tension and release. Texturally, modern composers used as few notes as possible, as they were striving for a bare sound. Only writing in the essential tones, musicians turned away from the Romantic period’s thick and involved texture.

To make music accessible for the whole nation, Russia created a style within Communism. Their music was called socialist realism, and was connected with life images that were expressed through exciting rhythms and flashy orchestral effects (Machlis 214). Late romantic composer Modest Mussorgsky (1839-1881) had said that "art is a means of communicating with mankind" (qtd. 214). Most famous of the modern Russian composers are probably Alexander Scriabin (1872-1915) and Sergei Rachmaninoff (1873-1943). Later, Sergei Prokofiev (1891-1953) and Dmitri Shostakovich (1906-1975) entered the Russian musical scene as prominent composers. Musicians like Rachmaninoff, Stravinsky, and Alexander Glazunov (1865-1936) left the Communist country, but others like Shostakovich, Armenian composer Aram Khatchaturian (1903-1978), and Dmitri Kabalevsky (1904-1987) stayed in Russia. In the 1930s, the opera Lady Macbeth of Mzensk by Shostakovich was attacked by the government. After World War II, Soviet theoretician Andrei Zhdanov demanded that Russian composers follow the 18th-century Classical masters, but composers had more freedom after the years of Stalin’s reign.

In England, Ralph Vaughan Williams (1872-1958) and Benjamin Britten (1913-1976) had an international impact, while Carl Orff (1895-1982), Kurt Weill, and Paul Hindemith influenced the Western world from a German point of view. But when Adolf Hitler’s Third Reich didn’t allow Hindemith’s music to be heard in concert, the composer left Germany and moved to the U.S., teaching composition at both Yale and Tanglewood. 20th-century Hungarian composers Béla Bartók and Zoltán Kodály fused their national style with folk music, while Leos Janácek from Czechoslovakia was a nationally known figure in teaching, conducting, and composing. Pianists and composers Isaac Albéniz (1860-1909) and Enrique Granados (1867-1916), provided modern Spanish music. From Finland came Jean Sibelius (1865-1957), with musical contributions also from Danish Carl Nielsen (1865-1931) and Swiss Ernest Bloch (1880-1959).

During the 19th century, American composers were influenced by Italian opera and the German symphony. Later in the Romantic period, French Impressionism had an impact on musicians in America who wanted to make their music as good in quality as that of the Europeans. Charles Edward Ives (1874-1954) is now considered the first truly 20th-century American composer with his expression of American style that fuses music from around the world, and New York-born pianist and composer Edward MacDowell (1861-1908) became quickly known in other countries. Other important American composers like Stephen Foster (1826-1864) and John Knowles Paine (1839-1906) taught music at Harvard University.

Before the historical stock market crash of 1929, the United States was financially stable during the 1920s. So, musicians received grants and fellowships to help support their interest in composition and performance.