Editing Tone cluster (section)

==Music theory and classification==
[[File:Piano-keyboard.jpg|thumb|upright=1.2|The modern [[Musical keyboard|keyboard]] is designed for playing a diatonic scale on the white keys and a pentatonic scale on the black keys. Chromatic scales involve both. Three immediately adjacent keys produce a basic chromatic tone cluster.]]

Prototypical tone clusters are chords of three or more adjacent notes on a [[chromatic scale]], that is, three or more adjacent [[Pitch (music)|pitches]] each separated by only a [[semitone]]. Three-note stacks based on [[Diatonic scale|diatonic]] and [[Pentatonic scale|pentatonic]] [[scale (music)|scales]] are also, strictly speaking, tone clusters. However, these stacks involve [[Interval (music)|intervals]] between notes greater than the half-tone gaps of the chromatic kind. This can readily be seen on a keyboard, where the pitch of each key is separated from the next by one semitone (visualizing the black keys as extending to the edge of the keyboard): Diatonic scales—conventionally played on the white keys—contain only two semitone intervals; the rest are full tones. In Western musical traditions, pentatonic scales—conventionally played on the black keys—are built entirely from intervals larger than a semitone. Commentators thus tend to identify diatonic and pentatonic stacks as "tone clusters" only when they consist of four or more successive notes in the scale.<ref>See Nicholls (1991), p. 155.</ref> In standard [[Classical music|Western classical music]] practice, all tone clusters are classifiable as [[secundal]] chords—that is, they are constructed from [[minor second]]s (intervals of one semitone), [[major second]]s (intervals of two semitones), or, in the case of certain pentatonic clusters, [[augmented second]]s (intervals of three semitones). Stacks of adjacent [[microtonal music|microtonal]] pitches also constitute tone clusters.<ref>Jones (2008), p. 91; Wilkins (2006), p. 145; Norman (2004), p. 47.</ref>

[[File:Thirteenth chord collapsed.png|thumb|A [[thirteenth chord]] collapsed into one octave results in a [[Consonance and dissonance|dissonant]] tone cluster<ref>Cope (2001), p. 6, fig. 1.17.</ref>[[File:Thirteenth chord collapsed.mid]]]]

In tone clusters, the notes are sounded fully and in unison, distinguishing them from [[ornament (music)|ornamented]] figures involving [[ornament (music)#Acciaccatura|acciaccaturas]] and the like. Their effect also tends to be different: where ornamentation is used to draw attention to the [[harmony]] or the relationship between harmony and [[melody]], tone clusters are for the most part employed as independent sounds. While, by definition, the notes that form a cluster must sound at the same time, there is no requirement that they must all ''begin'' sounding at the same moment. For example, in [[R. Murray Schafer]]'s choral ''Epitaph for Moonlight'' (1968), a tone cluster is constructed by dividing each choir section (soprano/alto/tenor/bass) into four parts. Each of the sixteen parts enters separately, humming a note one semitone lower than the note hummed by the previous part, until all sixteen are contributing to the cluster.<ref>Swift (1972), pp. 511–512.</ref>

[[File:Harmonic series spacing successive octaves.png|thumb|By the fourth [[octave]] of the [[harmonic series (music)|harmonic series]], successive harmonics form increasingly small [[second (interval)|seconds]] the fifth octave of harmonics (16–32)[[File:Tone cluster fifth octave harmonic series.mid]]]]

Tone clusters have generally been thought of as dissonant musical textures, and even defined as such.<ref>See, e.g., Seachrist (2003), p. 215, n. 15: "A 'tone cluster' is a dissonant group of tones lying close together...."</ref> As noted by Alan Belkin, however, instrumental [[timbre]] can have a significant impact on their effect: "Clusters are quite aggressive on the organ, but soften enormously when played by strings (possibly because slight, continuous fluctuations of pitch in the latter provide some inner mobility)."<ref>{{cite web|author=Belkin, Alan|url=http://www.musique.umontreal.ca/personnel/Belkin/bk.H/H6.html|title=Harmony and Texture; Orchestration and Harmony/Timbre|publisher=Université de Montréal|year=2003|access-date=2007-08-18 |archive-url = https://web.archive.org/web/20070622064614/http://www.musique.umontreal.ca/personnel/Belkin/bk.H/H6.html |archive-date = 2007-06-22}}</ref> In his first published work on the topic, [[Henry Cowell]] observed that a tone cluster is "more pleasing" and "acceptable to the ear if its outer limits form a consonant interval."<ref>Cowell (1921), pp. 112, 113.</ref> Cowell explains, "the natural spacing of so-called dissonances is as seconds, as in the overtone series, rather than sevenths and ninths....Groups spaced in seconds may be made to sound euphonious, particularly if played in conjunction with fundamental chord notes taken from lower in the same overtone series. Blends them together and explains them to the ear."<ref>Cowell, Henry (1969). ''New Musical Resources'', p.111-139. New York: Something Else. {{pre-ISBN}}.</ref> Tone clusters have also been considered noise. As [[Mauricio Kagel]] says, "clusters have generally been used as a kind of anti-harmony, as a transition between sound and noise."<ref>Kagel, Mauricio. "Tone-clusters, Attacks, Transitions", p.46. Cited in [[John Schneider (guitarist)|Schneider, John]] (1985). ''The Contemporary Guitar'', p.172. University of California. {{ISBN|9780520040489}}.</ref> Tone clusters thus also lend themselves to use in a percussive manner. Historically, they were sometimes discussed with a hint of disdain. One 1969 textbook defines the tone cluster as "an extra-harmonic clump of notes".<ref>Ostransky (1969), p. 208.</ref>