What is music? During the course of the history of Western music, many have tried to formulate an answer to the question of the ontology of music. In order to distinguish between music and non-music, repeated attempts have been made to compile a list of essential properties of music along with the necessary and sufficient conditions. It is not my intention to represent any or all of the expressed views on this matter in a systematic or all-encompassing order. Rather, I prefer to paint a brief and approximate picture of some of the problems that these attempts to define, determine, or discern music have encountered.
 'Musica ist eine Wissenschaft und Kunst, geschickte und angenehme Klänge klüglich zu stellen, richtig an einander zu fügen, und lieblich heraus zu bringen, damit durch ihren Wohllaut Gottes Ehre und alle Tugenden befördert werden [Music is a science and an art that produces dexterous and pleasant sounds, in order to combine them properly and present them charmingly so that their euphony may further God's honor and all virtues]', says composer and music theoretician Johann Mattheson. Philosopher Jean-Jacques Rousseau describes music as an 'art de combiner les sons d'une manière agréable à l'oreille [the art of combining sounds in a way that is pleasing to the ear]'. Organist and composer Johann Gottfried Walther thinks of music as 'die Ton-Kunst, d.i. die Wissenschaft wohl zu singen, zu spielen und zu componiren [the art of sound, i.e., the ability to sing, to play, and to compose well]'.
 Convinced of the difficulties that are involved in adequately defining music, music sociologists John Shepherd and Peter Wicke conclude that music itself is a discursively constituted category. That is, this term in itself can give rise to multiple, incommensurable and contested categories. 'The term 'music' is highly polysemous' (Shepherd and Wicke, p.208). (Musicologist Carl Dahlhaus no longer speaks of music (singular), but of 'musics'.)
 Another problem needs to be addressed. Judging by John Cage's composition, 4'33' (Play music), (among others) Levinson concludes: 'It should be apparent that there are no longer any intrinsic properties of sound that are required for something possibly to be music' (Levinson, p.271). According to Levinson, there are conditions essential to a piece being music that are not even directly audible. These observations, which are based on developments in musical language, can lead to a new definition of music inspired by the findings of the American philosopher, Arthur Danto. In his essay from 1964, 'The Artistic Enfranchisement of Real Objects: the Artworld', Danto acknowledges that the works of Marcel Duchamp and various Pop Art artists have made it impossible to separate art from non-art on the basis of formal qualities. Danto asks what will ultimately determine the difference between a Brillo box and a work of art consisting of a Brillo box? Danto's question amounts to the following: when one of two identical objects is considered art while the other is not, a certain context is assumed within which these two formally indistinguishable objects still enjoy their respective status. Danto calls this context the artworld: 'To see something as art requires something the eye cannot decry - an atmosphere of artistic theory, a knowledge of the history of art: an artworld' (Danto in Dickie & Sclafani, p.29). In 1974, George Dickie adds a sociological and pragmatic definition of a work of art to this notion of artworld: a work of art is a series of aspects (not every aspect of a work of art makes it a work of art) to which one or more individuals who act on behalf of the social institution artworld (e.g., the artist himself, presidents of art institutions, critics, aestheticians, etc.) grant the status of 'art' (cf. Dickie, p.35). Objects become works of art because (influential) people in the artworld have declared them to be works of art.
 I do not want to elaborate upon problems concerning all that, for convenience's sake, may be summed up as institutional or contextual theories. In Context, I point out certain problems dealing with the notion of context. The problem of demarcation (the problem of inside vs.outside) will recur in the institutional theories, for example, in determining who can be rated in the artworld and which series of aspects belong to the work of art.
 What is music? Not quite knowing where to start in the hermeneutic circle (Is that still important?), I will return to the thinkers who have committed themselves to determining the boundary between music and non-music, the boundaries between music, noise and silence. Despite the attention for the (cultural and temporal) context of music, despite artworld theories that result from this attention, defining music remains 'infected' from the inside by an intra-musical premise, a formalistic quality. All thinkers seem to concur that music, at any rate, has something to do with sound. (According to American composer Robert Ashley the 'most radical redefinition of music' would be one that defines music 'without reference to sound'.) Levinson: 'Perhaps the only thing that all theorists agree on is that music is necessarily sound' (Levinson, p.274). Nattiez: 'Sound is an irreducible given of music. Even in the marginal cases in which it is absent, it is nonetheless present by allusion ... The musical work manifests itself, in its material reality, in the form of sound waves' (Nattiez, p.67 and p.69). Although music is not limited to the acoustic dimension (There are other factors that determine whether or not something is music), we always speak of music in relation to sonority, according to Nattiez, even when it merely concerns a reference: sound is a minimal condition of music. To Shepherd and Wicke, it is the melodic, harmonic, rhythmic and timbrel configurations that lead us to recognize music as 'music' (cf. Shepherd and Wicke, p.10). They continue: 'We identified sound in music as the material medium that would ultimately guarantee music an integrity and relative autonomy as a specific signifying system' (Shepherd and Wicke, p.56). Ultimately, they define music as 'sounds 'in conversation' with sounds' (Shepherd and Wicke, p.200). Dahlhaus considers the musical work as 'tönender Sinnzusammenhang' [sounding coherence of meaning] (Dahlhaus, p.195, my italics). To musicologist Hans Heinrich Eggebrecht, specific to music is 'dasjenige, was sie im Reich des Tönens und Hörens ganz allein für sich selber hat' [that which it disposes of entirely by itself in the realm of sounding and hearing] (Dahlhaus, p.189). To Eggebrecht, audibility is an obvious aspect of music in which a distinction can be made between noise, sound, and tone. We are back to the definition of music as quoted by Jacques Attali in The Gift of Silence [donner les bruits], the introduction to this section: 'Music is inscribed between noise and silence' (Attali, p.19).
 Beginning with the idea that the definitions of music, noise and silence have (at least also) to do with (the absence of) sound, I will dedicate a number of pages to the investigation of the relationship between music and noise (Noise as Undifferentiated Sound and Noise as Undesirable Sound), and of the relationship between music and silence (Silence and/in Music). A separate page addresses a deconstruction of the oppositional pair, music-noise, as it (unconsciously) takes place in Jacques Attali's book, Noise (Music and/as (Dis)Order). One composer who has devoted nearly his entire musical life to the borders among music, silence and noise is John Cage. A number of pages are dedicated to his works and his views (Cage and Noise, and Cage and Silence). In the end, I intend to show how his compositions, 4'33'' and Waiting, deconstruct the opposition of silence and noise (Music, Noise, Silence, and Sound). On a separate page, thought is given to the ethics of a deconstruction of the borders between music, silence, and noise (Silence, Noise and Ethics). Finally, the pages on Cage may lead one to a page that connects silence to death (Silence and Death), and to a page on which Cage's use of silence is connected to French poet Stephane Mallarmé's interest in the color white (Cage, White, Mallarmé, Silence).