Karlheinz Stockhausen in the context of "Serialism"

Musique concrète (French pronunciation: [myzik kɔ̃kʁɛt]; lit. 'concrete music') is a type of music composition that utilizes recorded sounds as raw material. Sounds are often modified through the application of audio signal processing and tape music techniques, and may be assembled into a form of sound collage. It can feature sounds derived from recordings of musical instruments, the human voice, and the natural environment, as well as those created using sound synthesis and computer-based digital signal processing. Compositions in this idiom are not restricted to the normal musical rules of melody, harmony, rhythm, and metre. The technique exploits acousmatic sound, such that sound identities can often be intentionally obscured or appear unconnected to their source cause.

The theoretical basis of musique concrète as a compositional practice was developed by French composer Pierre Schaeffer, beginning in the early 1940s. It was largely an attempt to differentiate between music based on the abstract medium of notation and that created using so-called sound objects (French: l'objet sonore). By the early 1950s, musique concrète was contrasted with "pure" elektronische Musik as then developed in West Germany – based solely on the use of electronically produced sounds rather than recorded sounds – but the distinction has since been blurred such that the term "electronic music" covers both meanings. Schaeffer's work resulted in the establishment of France's Groupe de Recherches de Musique Concrète (GRMC), which attracted important figures including Pierre Henry, Luc Ferrari, Pierre Boulez, Karlheinz Stockhausen, Edgard Varèse, and Iannis Xenakis. From the late 1960s onward, and particularly in France, the term acousmatic music (French: musique acousmatique) was used in reference to fixed media compositions that utilized both musique concrète-based techniques and live sound spatialisation.

Electronic music broadly is a group of music genres that employ electronic musical instruments, circuitry-based music technology and software, or general-purpose electronics (such as personal computers) in its creation. It includes both music made using electronic and electromechanical means (electroacoustic music). Pure electronic instruments depend entirely on circuitry-based sound generation, for instance using devices such as an electronic oscillator, theremin, or synthesizer: no acoustic waves need to be previously generated by mechanical means and then converted into electrical signals. On the other hand, electromechanical instruments have mechanical parts such as strings or hammers that generate the sound waves, together with electric elements including magnetic pickups, power amplifiers and loudspeakers that convert the acoustic waves into electrical signals, process them and convert them back into sound waves. Such electromechanical devices include the telharmonium, Hammond organ, electric piano and electric guitar.

The first electronic musical devices were developed at the end of the 19th century. During the 1920s and 1930s, some electronic instruments were introduced and the first compositions featuring them were written. By the 1940s, magnetic audio tape allowed musicians to tape sounds and then modify them by changing the tape speed or direction, leading to the development of electroacoustic tape music in the 1940s in Egypt and France. Musique concrète, created in Paris in 1948, was based on editing together recorded fragments of natural and industrial sounds. Music produced solely from electronic generators was first produced in Germany in 1953 by Karlheinz Stockhausen. Electronic music was also created in Japan and the United States beginning in the 1950s and algorithmic composition with computers was first demonstrated in the same decade.

A tone cluster is a musical chord comprising at least three adjacent tones in a scale. Prototypical tone clusters are based on the chromatic scale and are separated by semitones. For instance, three adjacent piano keys (such as C, C♯, and D) struck simultaneously produce a tone cluster. Variants of the tone cluster include chords comprising adjacent tones separated diatonically, pentatonically, or microtonally. On the piano, such clusters often involve the simultaneous striking of neighboring white or black keys.

The early years of the twentieth century saw tone clusters elevated to central roles in pioneering works by ragtime artists Jelly Roll Morton and Scott Joplin. In the 1910s, two classical avant-gardists, composer-pianists Leo Ornstein and Henry Cowell, were recognized as making the first extensive explorations of the tone cluster. During the same period, Charles Ives employed them in several compositions that were not publicly performed until the late 1920s or 1930s, as did Béla Bartók in the latter decade. Since the mid-20th century, they have prominently featured in the work of composers such as Lou Harrison, Giacinto Scelsi, Alfred Schnittke and Karlheinz Stockhausen, and later Eric Whitacre. Tone clusters also play a significant role in the work of free jazz musicians such as Cecil Taylor, Matthew Shipp, and Kevin Kastning.

Aleatoric music (also aleatory music or chance music; from the Latin word alea, meaning "dice") is music in which some element of the composition is left to chance, or some primary element of a composed work's realization is left to the determination of its performer(s), or both. The term is most often associated with procedures in which the chance element involves a relatively limited number of possibilities.

The term became known to European composers through lectures by acoustician Werner Meyer-Eppler at the Darmstadt International Summer Courses for New Music in the beginning of the 1950s. According to his definition, "a process is said to be aleatoric ... if its course is determined in general but depends on chance in detail". Through a confusion of Meyer-Eppler's German terms Aleatorik (noun) and aleatorisch (adjective), his translator created a new English word, "aleatoric" (rather than using the existing English adjective "aleatory"), which quickly became fashionable and has persisted. More recently, the variant "aleatoriality" has been introduced.

Vocalists are capable of producing a variety of extended technique sounds. These alternative singing techniques have been used extensively in the 20th century, especially in art song and opera. Particularly famous examples of extended vocal technique can be found in the music of Luciano Berio, John Cage, George Crumb, Peter Maxwell Davies, Hans Werner Henze, György Ligeti, Demetrio Stratos, Meredith Monk, Giacinto Scelsi, Arnold Schoenberg, Salvatore Sciarrino, Karlheinz Stockhausen, Tim Foust, Avi Kaplan, and Trevor Wishart.

Olivier Eugène Prosper Charles Messiaen (UK: /ˈmɛsiæ̃/, US: /mɛˈsjæ̃, meɪˈsjæ̃, mɛˈsjɒ̃/; French: [ɔlivje øʒɛn pʁɔspɛʁ ʃaʁl mɛsjɑ̃]; 10 December 1908 – 27 April 1992) was a French composer, organist, and ornithologist. One of the major composers of the 20th century, he was also an outstanding teacher of composition and musical analysis.

Messiaen entered the Conservatoire de Paris at age 11 and studied with Paul Dukas, Maurice Emmanuel, Charles-Marie Widor and Marcel Dupré, among others. He was appointed organist at the Église de la Sainte-Trinité, Paris, in 1931, a post he held for 61 years, until his death. He taught at the Schola Cantorum de Paris during the 1930s. After the fall of France in 1940, Messiaen was interned for nine months in the German prisoner of war camp Stalag VIII-A, where he composed his Quatuor pour la fin du temps (Quartet for the End of Time) for the four instruments available in the prison—piano, violin, cello and clarinet. The piece was first performed by Messiaen and fellow prisoners for an audience of inmates and prison guards. Soon after his release in 1941, Messiaen was appointed professor of harmony at the Paris Conservatoire. In 1966, he was appointed professor of composition there, and he held both positions until retiring in 1978. His many distinguished pupils included Iannis Xenakis, George Benjamin, Alexander Goehr, Pierre Boulez, Jacques Hétu, Tristan Murail, Karlheinz Stockhausen, György Kurtág, and Yvonne Loriod, who became his second wife.

Richard Vance Maxfield (February 2, 1927 – June 27, 1969) was a composer of instrumental, electroacoustic, and electronic music.

Born in Seattle, Maxfield studied at Stanford University, University of California, Berkeley (with Roger Sessions) and privately with Ernst Krenek in Los Angeles. A Hertz Prize travel scholarship allowed Maxfield to travel to Europe, where he met Pierre Boulez, Karlheinz Stockhausen and Luigi Nono. In 1953 he studied at Tanglewood with Aaron Copland. In 1954–55 he studied at Princeton University with Sessions and his pupil Milton Babbitt. A Fulbright Scholarship allowed Maxfield to live in Europe between 1955 and 1957, where he studied with Luigi Dallapiccola and Bruno Maderna, lived for a brief period with Hans Werner Henze and met John Cage and David Tudor. In 1958, he attended Cage's courses at the New School for Social Research (now The New School). In 1959 he taught classes there himself, becoming the first American to teach purely electronic music (as opposed to electroacoustic music based on musique concrète-style recordings with microphones).

Henryk Mikołaj Górecki (/ɡəˈrɛtski/ gə-RET-skee; Polish: [ˈxɛnrɨk miˈkɔwaj ɡuˈrɛt͡skʲi] ; 6 December 1933 – 12 November 2010) was a Polish composer of contemporary classical music. According to critic Alex Ross, no recent classical composer has had as much commercial success as Górecki. He became a leading figure of the Polish avant-garde during the post-Stalin cultural thaw. His Anton Webern-influenced serialist works of the 1950s and 1960s were characterized by adherence to dissonant modernism and influenced by Luigi Nono, Karlheinz Stockhausen, Krzysztof Penderecki and Kazimierz Serocki. He continued in this direction throughout the 1960s, but by the mid-1970s had changed to a less complex sacred minimalist sound, exemplified by the transitional Symphony No. 2 and the Symphony No. 3 (Symphony of Sorrowful Songs). This later style developed through several other distinct phases, from such works as his 1979 Beatus Vir, to the 1981 choral hymn Miserere, the 1993 Kleines Requiem für eine Polka and his requiem Good Night.

Górecki was largely unknown outside Poland until the late 1980s. In 1992, 15 years after it was composed, a recording of his Symphony of Sorrowful Songs with soprano Dawn Upshaw and conductor David Zinman became a worldwide commercial and critical success, selling more than a million copies and vastly exceeding the typical lifetime sales of a recording of symphonic music by a 20th-century composer. Commenting on its popularity, Górecki said, "Perhaps people find something they need in this piece of music ... somehow I hit the right note, something they were missing. Something somewhere had been lost to them. I feel that I instinctively knew what they needed." This popular acclaim did not generate wide interest in Górecki's other works, and he pointedly resisted the temptation to repeat earlier success, or compose for commercial reward.