It is clear that musicians know about silence in music. Empty bars or parts of bars occur in virtually every musical piece. Rests are an inseparable part of any composition. On a more modest and subtle level, silences mark the transition from one musical sentence to the next by way of caesura. Silence also demarcates the beginning and the end of a piece of music.
In musical theory, silence is not always referred to as the point where musical sounds actually cease to exist. Moments of silence are experienced during sustained fermates, extreme pianissimo's, or when a complex harmony dissipates into a sparing use of the tone material. One becomes aware of silence in music that 'sound from afar', usually indicated by the instruction 'come da lontano'. (A great amount of music by Russian composer Alfred Schnittke opens and closes with scarcely audible sounds. His music resides between the not-yet-audible and the no-longer-audible. It seems as though his music is already there before the listener can hear it and continues to resound long after the listener has registered the last tones. Through this 'non-ceasing' music, which resounds beyond the limits of its audibility, silence acquires a different form of musical Dasein.)
 This brief and incomplete summary immediately shows the heterogeneity of silence. Silence and silence do not necessarily match. For that reason alone, silence deserves more attention. As Martin Zenck concludes in 'Dal niente - Vom Verlöschen der Musik' [On the Extinguishing of Music], however, the attention to silence is a peripheral moment in composition and music analysis. By no means is its status equal to sound (cf. Zenck, p.15). The pause in music, identified as an absence of sound, is the exception to the rule that has music designated as the center of the musical spectrum. Eduard Hanslick's famous definition of music as 'die tönend bewegte Form' ['form propelled by sound'] in no way indicates a music that is present in its absence, in non-sound. Sound and silence relate to each other as the essential versus the supplement, as the primary versus the secondary. It seems that not the tritonus (the augmented fourth), but rather silence is the true 'diabolus in musica' in Western music. Contrary to the tritonus, silence was never banned, but its raison d'etre has been thoroughly questioned up until the 20th century. Its function was mainly dramatic or rhetoric. Silence is subordinate to sound, and has for the longest time (still?) been regarded as something less significant.
 An example of how silence remains secondary to sound and music in the theory of music can be found in Thomas Clifton's essay 'The Poetics of Musical Silence'. 'To focus on the phenomenon of musical silence is analogous to deliberately studying the spaces between trees in a forest: somewhat perverse at first, until one realizes that these spaces contribute to the perceived character of the forest itself, and enable us to speak coherently of 'dense' growth or 'sparse' vegetation. In other words, silence is not nothing. It is not the null set. Silence is experienced both as meaningful and as adhering to the sounding position of the musical object' (Clifton, p.163, my italics). Clifton seems to focus our attention on the meaning of silence within music. In a certain sense, an emancipatory move. Upon closer consideration, however, this reading loses significant cogency. Clifton leaves the traditional relationship between sound and silence intact. He continues to operate within the existing hierarchy where silence serves sound. Similar to the spaces between trees, silences that surround tones enable us to hear the sounds. 'The significance of silence is therefore contingent upon a sounding environment', Clifton continues (Clifton, p.163). Silence remains dependent on the world of sound because it is only there that it can acquire meaning. In a summary of the various ways in which silence can function, Clifton discusses 'examples of the way silence is used to express how the music is speaking' and 'the adherence of silence to the grammar of the musical statement' (cf. Clifton, p.173). In both cases, silence is clearly still in the service of sound. Clifton does try to convince his readers of the importance of silence within music, but this importance ultimately serves the sounds, the music. Silence is no longer empty, that is to say, without meaning, but its autonomy - i.e., its non-sound based value - is left unrecognized.
 At the start of the 20th century, the composers of the Second Viennese School, Arnold Schönberg, Anton Webern, and Alban Berg shared a similar outlook on silence. Still, signs of a changing attitude towards silence can be found here. Many compositions by Berg lack a clear closure; rather, they fade into a distance, a void, an infinitude. With that, Berg joins the tradition of many composers from the Romantic era who worked with sounds 'come da lontano', sounds that originate in the distance, thereby suggesting a certain infinity. Even when we no longer hear sounds, the music is still present. However, Berg still thinks of silence as a special and peripheral moment. It only becomes apparent in very special areas of his music, particularly towards closures. And can we maintain that Berg emancipates silence? Clifton rather describes the experience of Berg's fading tones as a sensation of resistance toward the moment when the music will reside only in recollection (cf. Clifton, p.175).
Is silence frightening? Does it make us think back longingly to the moments when it was filled with musical sounds?
 With Webern, too, sound remains the primary aspect of composing even though the presence of multiple rests within his works disperses the sound to a great extent. However, this does not seem to be the result of an intended use or a conscious emancipation of silence, but of the way in which the tone material is processed. Dedication to a previously chosen twelve-tone row implies that variation is primarily reserved for the rhythmic part. It is obvious that rests will then play a more important role (cf. Veselinovic-Hofman, p.4). Nevertheless, Webern's work definitely presents an emancipatory moment with regard to silence. In his Variationen für Klavier, opus 27, for example, he treats silence as sound: the performer is instructed to speed up during a rest before pausing. (I am referring to the third part of the composition, bars 43-45. An accelerando in bar 43 is maintained in the silent bar 44. The initial tempo is taken up again in bar 45 that begins with a rest.)
 A third example. Schönberg. Is silence structurally revalued in his Sechs kleine Klavierstücken, Opus 19, no.2 (Play music)? The piece begins with a rest. A rest after silence, after the silence that is outside the composition, after the solemn silence with which the piece is welcomed. (Below the score, Schönberg indeed asks for a long pause after each movement, a pause that is not motivated by considerations of performing practice.) This rest is not an accidental phenomenon or a necessary respite, but an event deliberately considered in the framework of the composition (cf. Veselinovic-Hofman, p.3). The rests that alternate with the third g-b in the rhythmic motif from bar 1 (a pianissimo third on the border of audibility) form an essential part of the musical sentence. When the sounding third breaks the silence, and the silence in turn breaks the sound, the two engage in a mutual relation that knows no hierarchical distinction. Still, a problem remains. This line of reasoning can only be sustained as long as one knows the score. Veselinovic-Hofman rightfully points out that the first pause cannot immediately be recognized as a musical moment, a moment within the composition, through listening (cf. Veselinovic-Hofman, p.3). Even though the rest serves a structural function within the work, the listener who is not familiar with the score will most likely assume Opus 19, no.2 (Play music) starts with the first sounding third at the second beat of the first bar. (It seems that the listener only becomes aware of the importance and impact of silence - silence regarded as the absence of 'musical' sounds within a musical work - when these sounds are extremely delayed as in John Cage's composition Waiting) (Play music.) The opening rest in Opus 19, no.2 (Play music) becomes significant at the moment when sound occurs; therefore, according to Veselinovic-Hofman, silence remains supplementary to sound. The change that takes place in this piece, however - a change that is noticeable only when the score is studied (and possibly kept in memory during a subsequent listening) - is that the rest acts essentially supplementary with respect to its hierarchical relation to sound. The rest remains subordinate to the 'musical' sounds, but no longer functions as an amorphous, meaningless silence; the significance of the rest is the absence of sound (cf. Veselinovic-Hofman, p.4).
Silence remains supplementary to sound in Opus 19, no.2 (Play music). The rests in this composition by Schönberg signify the absence of sound. Although they are 'essentially supplementary', the hierarchical order remains intact. But can something else also be heard in this work? Is another reading possible? A cautious proposal. Schönberg makes us aware of the idea that music does not necessarily need to start with a tone or a sound, that there is silence before, after and in or during music, that silence is music. Is silence subordinate to sound within Schönberg's composition, or does sound require silence in order to manifest itself as sound? When the repeating thirds slowly and waveringly join a field of silence, they may very well signify a reversal of the hierarchically ordered system. The music defines itself by what it is not (silence, non-music). Sound becomes a special moment in the world of silence. As the white on a page is necessary for the words or notes on that page to appear, so silence is the precondition for sound. However, the white is not only the pureness of the blank page. It is also the space between the notes, the dimension within which lateral connections between notes take place (cf. Cage, White, Mallarmé, Silence) . Analogously, it is only through silence that the difference between separate sounds can be experienced. Silence immediately resides within the musical domain. Music is always already permeated by silence. Music is also silence. Perhaps we just never (consciously) heard the silence in music.
 According to Zenck, the 20th century exhibits a radical change of the paradigm according to which theorists and composers appreciate the hierarchical relation between sound and silence. I am not concerned with passing final judgment on whether or not this change takes place in Opus 19, no.2 (Play music), or whether Schönberg's composition is the first in which a reversal in the hierarchical relation between sound and silence possibly takes place. The extensive presence of rests and silence in his composition enables one to read Opus 19, no.2 (Play music) with this possible reversal in mind. First reading: sound above silence. Silence assumes its contours through sounds that outline its boundaries (make it sound). Something needs to sound in order to know that there is silence in between or around. Second reading: silence above sound. Analogous to the idea that in a material sense, it is the spaces between the words that make a text possible as a text, silence constitutes the condition for the musical sign. It is a space that provides a condition for music to spread, a Da-sein that promotes the development of sounds. 'What makes a wheel a wheel is the space between the spokes' (Lao-Tse).
Many 20th century composers have brought the long-lasting order in the hierarchy of sound and silence into question. A great deal of music is sufficiently ready to realize an inversion of this hierarchical position at the level of the compositional process. Two examples on this website. In Cage and Silence, I expand this idea on the basis of a work by John Cage. And in No (-) Music, several 'silent' works of German composer Dieter Schnebel are discussed. His Nostalgie: Solo für 1 Dirigenten, a silent solo for one conductor, opens up the visual, i.e. non-audible, potential of music. His book MO-NO. Musik zum Lesen [MO-NO. Music To Read] contains signs (drawings, texts, graphic scores) that incite the reader (listener?) to compose and to hear imaginary music, thereby opening the domain of the un-heard, the merely imagined-heard, the domain of inaudibility and silence, to the realm of music.
A third example is discussed below.
 More or less by coincidence, more or less at random, I will focus on a string quartet by Italian composer Luigi Nono entitled, Fragmente - Stille, An Diotima) (Play music). This piece hovers between sound and silence. In other words, the sound is mediated by non-sound while the silence is mediated by sound. This enables a twofold reading: one that takes sound as the primary aspect of the work; the other starts from silence with sound as its supplementary component.
Fragmente - Stille, An Diotima) (Play music) consists of short fragments that are separated by long silences. Both the title and the score make one suspect that silence occurs where the music fades away during long fermates and pauses. (The tempi are indicated with extreme accuracy throughout the score. However, the fast tempo changes and the large number of silences immediately negate this metrical recording.) The silence spreads in between the fragments with the result that the composition becomes extremely discontinuous. It seems as though all these fragments are attempts to emerge from a no-longer-wholeness or not-yet-wholeness to something more substantial, something longer, an uninterrupted unity. The constantly appearing silences prohibit the sound islands from growing together to a greater whole.
However, by listening to the music and studying the score, one can hear and see something entirely different. The stability of the first interpretation is undermined. No longer assuming sound to be the primary aspect, but rather, starting from silence this work does not consist of bits of music whose continuity is constantly disrupted. When rest, quietness and silence become the norm and sounds make up the secondary element, this work actually proves to display another discontinuity. It is not so much the silence that works its way between the sounding fragments; rather, the sounds break the ongoing silence. In other words, the less we hear the closer the music reaches the inaudible, and the more continuous the work becomes. This also emphatically shows in the often hesitating tones, tones without vibrato, or tones that are produced without a strong bow. The silence seems to pervade the sound here, becoming audible with the sound as a shadow or a specter. (To return to the primary attention to sounds for a moment: when the conventional sound of a string quartet appears, there is still something new to be heard: the quality of this sound to which normal perception has long become accustomed can again be experienced consciously in this context. No longer are the 'unusual' sounds in Fragmente - Stille, An Diotima) (Play music) deviations from the norm. Rather, the conventional bow techniques strike one as particularities within a multitude of sound options.)
The silence generates the continuity that is at times interrupted by the sounds. With regard to the sound fragments, this could mean that we allow the fragments to remain as fragments without having them dissipate into a larger sounding unity (In an essay on Nono and Hölderlin, Peter Andraschke points out that 'Fragmente' may also hint at the bits of text by Hölderlin that Nono uses. Wrenched from their 'original' context, they acquire a new openness in the domain of the silence. It is there that their heterogeneous character reveals itself without being adopted into a new meaningful construct, precisely because they are indeed not being adopted into a new, meaningful construct. Text and music are not unambiguously interrelated; they do not by any means 'read' or reflect each other. Hölderlin's text fragments are not recited nor sung. They are merely present as concealed fragments in the silence that is neither silent nor meaningless. They are just there, at the top of the pages, accompanying almost every bar number, inside the musical work, but at the same time on the outside. They are just there for the performers, but should not be taken as programmatic performance indications.) Fragmente - Stille, An Diotima) (Play music). No sustained development. No ongoing increase nor decrease of suspense. No tension curve for the ear to be clearly observed. The title of the piece does not suggest some other, complete work. It does not forget the silence as its place of birth. It remains connected to that dimension throughout. However, this is not self-evident to Nono, nor does he consider it an easy task. Silence, to him, is intangible. It cannot be manipulated; it is what escapes his power. The composer has to allow a force that escapes his intentions and active contributions precisely in the space where he would want to be in charge: the world of the sounds.
Silence assumes a different quality in this second reading. It is no longer the temporal absence of sound. ('There is more sound volume in many silences than in a fortissimo from a Beethoven piece', Nono states.) Rather, it is an open space from which new sounds can emerge again and again. In this sense, silence can join the fragments. Until the next fragment, the listener has the opportunity to listen again to the sounds in his memory that have already faded. With that, the 'absence of sounds' becomes at least equally important as the sounds themselves. According to Nono, this space of silence is not amorphous. It can be experienced differently every time it is heard with a susceptible fantasy for dreamy spaces, for sudden ecstacies, for unspeakable thoughts, for quiet breathing and for the silence of timeless singing (cf. Nono's preface to the string quartet). Different sounds emerge from these constantly changing silences. However, it is silence - the 'absence of the sound' that is not a nothingness and that should not be thought of as an absence - that deserves attention for this very reason. All silences (in Fragmente - Stille, An Diotima) (Play music) are different and all are filled with their own meanings. They are there to be listened to (cf. Zenck, p.20-1. cf. Broers, p.302-5).
 The encounter with this process of listening, the encounter with silence, can be considered a principal idea of Fragmente - Stille, An Diotima) (Play music). Music itself accomplishes the rearrangement or reversal of the initial conceptual hierarchy between sound and silence. A deconstructive strategy. Deconstruction at work within music.