Pierre Schaeffer in the context of "Experimental musical instrument"

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.

Experimental music is a general label for any music or music genre that pushes existing boundaries and genre definitions. Experimental compositional practice is defined broadly by exploratory sensibilities radically opposed to, and questioning of, institutionalized compositional, performing, and aesthetic conventions in music. Elements of experimental music include indeterminacy, in which the composer introduces the elements of chance or unpredictability with regard to either the composition or its performance. Artists may approach a hybrid of disparate styles or incorporate unorthodox and unique elements.

The practice became prominent in the mid-20th century, particularly in Europe and North America. John Cage was one of the earliest composers to use the term and one of experimental music's primary innovators, utilizing indeterminacy techniques and seeking unknown outcomes. In France, as early as 1953, Pierre Schaeffer had begun using the term musique expérimentale to describe compositional activities that incorporated tape music, musique concrète, and elektronische Musik. In America, a quite distinct sense of the term was used in the late 1950s to describe computer-controlled composition associated with composers such as Lejaren Hiller. Harry Partch and Ivor Darreg worked with other tuning scales based on the physical laws for harmonic music. For this music they both developed a group of experimental musical instruments. Musique concrète is a form of electroacoustic music that utilises acousmatic sound as a compositional resource. Free improvisation or free music is improvised music without any rules beyond the taste or inclination of the musician(s) involved; in many cases, the musicians make an active effort to avoid clichés; i.e., overt references to recognizable musical conventions or genres.

Acousmatic sound is sound that is heard without an originating cause being seen. The word acousmatic, from the French acousmatique, is derived from the Greek word akousmatikoi (ἀκουσματικοί), which referred to probationary pupils of the philosopher Pythagoras who were required to sit in absolute silence while they listened to him deliver his lecture from behind a veil or screen to make them better concentrate on his teachings. The term acousmatique was first used by the French composer and pioneer of musique concrète Pierre Schaeffer. In acousmatic art one hears sound from behind a "veil" of loudspeakers, the source cause remaining unseen. More generally, any sound, whether it is natural or manipulated, may be described as acousmatic if the cause of the sound remains unseen. The term has also been used by the French writer and composer Michel Chion in reference to the use of off-screen sound in film. More recently, in the article Space-form and the acousmatic image (2007), composer and academic Denis Smalley has expanded on some of Schaeffers' acousmatic concepts.Since the 2000s, the term acousmatic has been used, notably in North America to refer to fixed media composition and pieces.

In musique concrete and electronic music theory the term sound object (originally l'objet sonore) is used to refer to a primary unit of sonic material and often specifically refers to recorded sound rather than written music using manuscript or a score. It was coined by Pierre Schaeffer in his publication Traité des objets musicaux (1966).

Luc Ferrari (5 February 1929 – 22 August 2005) was a French composer of Italian heritage and a pioneer in musique concrète and electroacoustic music. He was a founding member of RTF's Groupe de Recherches Musicales (GRMC), working alongside composers such as Pierre Schaeffer and Pierre Henry.

In music, tape loops are loops of magnetic tape used to create repetitive, rhythmic musical patterns or dense layers of sound when played on a tape recorder. Originating in the 1940s with the work of Pierre Schaeffer, they were used among contemporary composers of 1950s and 1960s, such as Éliane Radigue, Steve Reich, Terry Riley, and Karlheinz Stockhausen, who used them to create phase patterns, rhythms, textures, and timbres. Popular music authors of 1960s and 1970s, particularly in psychedelic, progressive and ambient genres, used tape loops to accompany their music with innovative sound effects. In the 1980s, analog audio and tape loops with it gave way to digital audio and application of computers to generate and process sound.