Around 1900, many composers felt that the rules of Western music – major and minor keys, regular metres, the orchestra as the main source of sound – had been explored as far as they could go. The 20th century became an age of experiment. Some composers abandoned keys altogether; some let chance decide the notes; some built whole pieces from tiny repeating patterns; and some made music from electronic circuits and recorded noises. Music that deliberately pushes boundaries like this is called avant-garde (French for “advance guard”).

Main characteristics of 20th-century avant-garde and modern music

• Radical and diverse tastes – unconventional rhythms, sounds and melodic patterns; many different styles existing side by side.
• New sound sources – electronic instruments, recorded sounds, prepared pianos, everyday objects and silence itself were accepted as music.
• Thicker, more varied harmony – more dissonance, polytonality (two keys at once) and atonality (no key at all).
• Steady driving pulse and repetition – especially in minimalism, where short rhythmic and melodic patterns repeat and change slowly.

Key movements and ideas

Impressionism

Claude Debussy (1862–1918) wanted music to suggest moods and images, like the blurred light in Impressionist paintings. He used the whole-tone and pentatonic scales, floating chords and soft, shimmering timbres, as in Prélude à l’après-midi d’un faune (1894) and Clair de lune.

Atonality and serialism

Arnold Schoenberg (1874–1951) began writing atonal music with no home key. In the 1920s he devised the twelve-tone or serial method: the composer arranges all twelve notes of the chromatic scale into a fixed order called a tone row, and builds the piece from that row – forwards, backwards, upside down and transposed – so that no note becomes the “tonic”. His pupils Alban Berg and Anton Webern developed the method further.

Rhythm and primitivism

Igor Stravinsky’s ballet The Rite of Spring (1913) shocked its first audience with pounding, irregular accents, changing metres, polyrhythms and harsh dissonance.

Aleatory (chance) music

Aleatory music (from the Latin alea, dice) leaves some parts of the music to chance or to the performer’s choice. John Cage (1912–1992) used coin tosses and the Chinese I Ching to choose notes, and in 4′33″ (1952) the performers play nothing for four minutes and 33 seconds: the “music” is the sound of the hall and the audience. Watch the Berlin Philharmonic perform it – and listen to the room.

Minimalism

From the 1960s, American composers such as Terry Riley, Steve Reich and Philip Glass built music from short patterns repeated many times with gradual changes, over a steady pulse. In Reich’s Clapping Music (1972), two performers clap the same 12-beat pattern; after every few repeats, one performer shifts the pattern by one beat, so the two parts drift out of line and back together.

Electronic music

The theremin (1920s), played without touching it, was one of the first electronic instruments. After the Second World War, composers made musique concrète from recorded sounds on tape, and in the 1960s Robert Moog’s synthesiser made electronic sound available to pop musicians as well. Today, almost all popular music – including soca and dancehall – is produced with electronic tools.

Try it: 20th-century sound experiments

Compare a tonal tune with a twelve-tone row and a whole-tone scale. Then play the phasing clap pattern, inspired by Clapping Music, and use the tempo slider to speed it up.

Jazz meets the concert hall: George Gershwin

George Gershwin (1898–1937) was a New York songwriter who brought jazz and blues into concert music. His Rhapsody in Blue (1924) for piano and orchestra opens with a famous clarinet glissando and mixes blue notes, syncopation and big Romantic melodies. He also wrote the opera Porgy and Bess (1935), which includes “Summertime”, and many Broadway musicals – an important part of 20th-century music theatre.

Activity: compose a chance piece

1. Write the numbers 1–6 next to six different sounds you can make in class (clap, click, stamp, hum, tap a desk, whistle).
2. Roll a die eight times to decide the order of the sounds; that is your aleatory “score”.
3. Perform it, then roll again for a completely different piece. How does it feel to let chance compose?

Quick check

1. What does “atonal” mean?

Show answer

Music with no home key or tonic.

2. What is a tone row in serial music?

Show answer

An ordered arrangement of all twelve chromatic notes that the composer uses to build the piece.

3. What is aleatory music? Give an example.

Show answer

Music in which some elements are left to chance or the performer’s choice – for example John Cage’s 4′33″.

4. Name two features of minimalism.

Show answer

Short repeated patterns, gradual change and a steady pulse.

5. How did George Gershwin combine different styles?

Show answer

He mixed jazz and blues (blue notes, syncopation) with classical forms, as in Rhapsody in Blue and the opera Porgy and Bess.

Previous: The Romantic Period (c. 1820–1900): Beethoven, Schubert, Berlioz, Clara Schumann and Tchaikovsky

Next: Western Art Music Forms: Opera, Oratorio, Cantata, Chorale, Concerto, Sonata, Symphony, Minuet and Trio, and More

Syllabus link: NCSE: not covered (CSEC only). CSEC® Music syllabus (CXC 31/G/SYLL 17), Section 1: Listening and Appraising – Music History and Theory: Specific Objectives 1, 2 and 6; Content 2(e)(i)–(iv) (20th-century avant-garde/modern characteristics), 3(a)(ii) (serial music, tone poem, music theatre) and 6(d) (George Gershwin); listed styles: avant-garde aleatory music (2025–2027), serial music (2031–2033).

Attributions to media used in this post:

Steve Reich.jpg – Ian Oliver – CC BY 2.0 (via Wikimedia Commons)

Bob Moog3.jpg – Moog Music / Norlin – Public domain (via Wikimedia Commons)

Theremin trio (better B&W).jpg – Unknown photographer – Public domain (via Wikimedia Commons)

© 2026 Vedesh Kungebeharry. All rights reserved.