Makis Solomos
translation from the French: Jennifer Higgins

Possibly the most important musical revolution of the 20th and 21st centuries has been the emergence of sound, and the ever-greater importance accorded to it (see Solomos 2019). Xenakis occupies a special place in this development, whereby, to put it simply, composition of sound has tended to take the place of compositions with sound. From the 1950s onwards, with instrumental works such as Le Sacrifice (1953), Metastaseis (1953-1954), and Pithoprakta (1955-1956), and electroacoustic pieces such as Diamorphoses (1957) and Concret PH (1958), he developed a conception of music focused on sound.

Xenakis himself did not theorise this new conception of composition: we know that most of his theoretical work was related to the question of the formalisation of music. However, we need only listen to his music, allow ourselves to be carried by its sensations – without seeking mathematical formulae in the sound masses that shape it, whether or not these formulae are actually present – to realise that not only is there an individual Xenakis sound (forte intensities, extreme registers, glissandi, etc.) but also that the music takes hold of us, seizes us from all sides; we are submerged in it: the music’s energy is that of sound functioning as a vast envelope, like a rough ocean.

Much of Xenakis’s music, both instrumental and electronic, can be listened to and analysed as composed sound, as a sonic synthesis transposed onto the temporal scale of the work. Some of his pieces are very explicit on this point, such as his two last electronic pieces, composed with the GENDYN program, Gendy3 (1991) and S.709 (1994). An algorithm synthesises the sound continuously, using probabilistic variations of its pressure curve (see Stochastic synthesis). There is thus no difference, strictly speaking, between synthesis (of sound) and composition (in the traditional sense): in theory, composition is the direct result of synthesis – in Xenakis’s conceptual language, macrocomposition results from microcomposition (see Xenakis 1981). The granular concept of sound that Xenakis developed in the late 1950s is also very revealing (see Granular synthesis). Lacking the means to put granular synthesis into practice at the time, he proposed the hypothesis of a “second order sonority” (Xenakis 1992, 103) and composed Analogique A and B (1958-1959) to test it: the nine string instruments play only isolated sounds (short arco notes, pizzicati or battuti col legno) and the tape (Analogique B) is made with clouds of very short sinusoidal sounds; these isolated instrumental sounds and these sinusoidal sounds represent the grains of sound and Xenakis hopes that the ear will fuse them and hear an overall sound (see Di Scipio 1999). This hypothesis implies that composition (of the whole work) is a synthesis (of sound) on a higher level.

The compositions discussed here represent exceptions in Xenakis’s oeuvre. In general, his work does not consist of a macrocomposition taken, unmediated, from the microcomposition, or of compositions that simply transpose a sound synthesis, not least because most of his oeuvre (in quantitative terms) is instrumental and therefore does not draw on synthesis or microcomposition. It can nevertheless be demonstrated that a large proportion of his music can easily be analysed as composed sounds. One simply needs to replace the word sound with sonority, in order to indicate that the composed object in question is not sound in the physical sense of the word, but a more complex entity, for example the whole section of an orchestral work.

The beginning of Jonchaies (1977) is a good example. The passage between ms.10 and 62, where the strings play (with a few percussion instruments), forms a long, almost monolithic section, with a very clear gradual interior evolution, just like the evolution of a single sound. The strings are divided into eighteen parts, played by one or two instruments. Despite lasting for a long time, the trajectory is very sustained, and schematic enough for the ear to follow from start to finish, as the eye would follow a visual outline of the piece (cf. the transcription in the form of a graph given in Harley 2001, 41). Furthermore, the whole passage is based on a single sieve (see Sieve theory), or scale (which, according to Xenakis, is drawn from the pelog scale; see Varga 1996, 162). But the key element is not the scale itself, as a series of pitches. Pitch is not a principal characteristic here: given that it is stretched out over a piece that lasts for such a long time, that it is explored patiently over its whole range in such a linear way, and that it is placed within the gigantic sound halo produced by the technique of heterophony, we can conclude that the sieve is used for its color. To sum up, we can see this passage as a single sound that gradually unfurls, and whose internal composition and temporal evolution we can examine as if under a microscope and in slow motion.

As we know, Xenakis often used graph paper to “draw” his music and create plastic forms, a method that reinforces the visual (two-dimensional) aspect of evolution in time and, thus, the sound dimension itself. One striking and well-known example is that of bars 52-59 of Pithoprakta: for these few bars, he used Gauss’s law to calculate over a thousand speeds, or glissandi (1142, according to the historic article in Gravesaner Blätter: Xenakis 1956, 31; 1148 according to Musiques formelles: Xenakis 1963, 30 [English translation: Xenakis 1992, 15]; 1146 according to my own count). However, these glissandi are distributed over time thanks to a famous graph, of which two versions exist (see Gibson 1994). The overall result – the sonority – is, according to Xenakis’s own comments, “a plastic modulation of the sonic material” (Xenakis 1956, 31; our translation), and, we could add, a modulation resulting directly from the form of the graph. There are in fact two versions of the article in which Xenakis makes this statement (as we have already seen in relation to the differing counts of glissandi). In the older one he states that “the distribution [of the speeds: that is, the calculation of their values] is Gaussian, but the geometric form [that is, their positioning using the graph] is a plastic modulation of the sonic material” (Xenakis 1956; our translation). This is the hypothesis adopted here. In the second article he writes: “the distribution being Gaussian, the macroscopic configuration is a plastic modulation of the sonic material” (Xenakis 1992, 15), which implies that the graph is drawn from the calculation.

There are many other works in which Xenakis uses graphs to develop linear glissandi, Brownian motion (see Random walk), arborescences, etc. Whether composed with or without graphs, most of Xenakis’s works can be analysed as successions of sonorities, that is, as sections that we listen to as composed sounds. The arrangement (the shape) can be decided according to a logic of process composition, a dramatic evolution, or another method. It is important to remember that the approach proposed here does not claim to be exclusive. Listening to a work by Xenakis as a series of composed sounds, or of sonorities, does not mean that one cannot also hear its rhythmic or dramatic qualities, or take an interest in questions of formalisation and mathematics.


This text was first published in French with the title “L’invention du son” in Solomos, Makis (ed.). 2022. Révolutions Xenakis, 160-63. Paris: Philharmonie de Paris / Éditions de l’Œil.


Di Scipio, Agostino. 1999. “The Problem of 2nd-Order Sonorities in Xenakis’ Electroacoustic Music.” Organised Sound 2 (3): 165-178.

Gibson, Benoît. 1994. “La théorie et l’œuvre chez Xenakis: éléments pour une réflexion.” Circuits 5 (2): 42-46.

Harley, James. 2001. “Formal Analysis of the Music of Iannis Xenakis by Means of Sonic Events: Recent Orchestral Works.” In Presences of Iannis Xenakis / Présences de Iannis Xenakis, edited by Makis Solomos, 37–52. Paris: Cdmc.

Hoffmann, Peter. 2009. “Music Out of Nothing? A Rigorous Approach to Algorithmic Composition by Iannis Xenakis.” PhD diss. Berlin: Technischen Universtät Berlin.

Solomos, Makis. 2019. From Music to Sound. The Emergence of Sound in 20th- and 21st-Century Music. London: Routledge.

Varga, Bálint A. 1996. Conversations with Iannis Xenakis. London: Faber and Faber.

Xenakis, Iannis. 1956. “Wahrscheinlichkeitstheorie und Musik.” Gravesaner Blätter 6: 28-34.

Xenakis, Iannis. 1963. Musiques formelles. Nouveaux principes formels de composition musicale. La revue musicale n°253-254. Paris: Richard-Masse.

Xenakis, Iannis. 1981. “Les chemins de la composition musicale.” In Xenakis, Iannis. 1994. Kéleütha, texts compiled by Alain Galliari, preface and notes by Benoît Gibson, 15-38. Paris: L’Arche.

Xenakis, Iannis. 1992. Formalized Music: Thought and Mathematics in Composition, revised edition, additional material compiled and edited by Sharon Kanach. Stuyvesant (NY): Pendragon Press.

How to cite

SOLOMOS, Makis. 2023. “Sonority,” translated by Jennifer HIGGINS. In A Xenakis Dictionary, edited by Dimitris Exarchos.