Editing Music theory (section)

===Chord===
{{Main|Chord (music)}}
[[File:C triad.svg|thumb|upright=0.7|C major triad represented in [[staff notation]].<br />{{Audio|Just major triad on C.mid|Play}} in [[just intonation]]<br />{{Audio|Major triad on C.mid|Play}} in [[Equal temperament]]<br />{{Audio|Quarter-comma meantone major chord on C.mid|Play}} in [[Meantone temperament|1/4-comma meantone]]<br />{{Audio|Young temperament major chord on C.mid|Play}} in [[Young temperament]]<br />{{Audio|Pythagorean major chord on C.mid|Play}} in [[Pythagorean tuning]] ]]
A chord, in music, is any [[harmony|harmonic]] set of three or more [[Musical note|note]]s that is heard as if sounding [[Simultaneity (music)|simultaneously]].{{sfn|Benward and Saker|2003}}{{rp|pp. 67, 359|quote=A chord is a harmonic unit with at least three different tones sounding simultaneously." "A combination of three or more pitches sounding at the same time.}}{{sfn|Károlyi|1965|}}{{rp|p. 63|quote=Two or more notes sounding simultaneously are known as a chord.}} These need not actually be played together: [[arpeggio]]s and broken chords may, for many practical and theoretical purposes, constitute chords. Chords and [[Chord progression|sequences of chords]] are frequently used in modern Western, West African,{{sfn|Mitchell|2008}} and Oceanian{{sfn|Linkels|n.d.|loc={{Page needed|date=July 2015}}<!--Specific page citation within this twelve-page article needed.-->}} music, whereas they are absent from the music of many other parts of the world.{{sfn|Malm|1996}}{{rp|p. 15|quote=Indeed this harmonic orientation is one of the major differences between Western and much non-Western music.}}

The most frequently encountered chords are [[Triad (music)|triads]], so called because they consist of three distinct notes: further notes may be added to give [[seventh chord]]s, [[extended chord]]s, or [[added tone chord]]s. The most [[Common chord (music)|common chord]]s are the ''[[major chord|major]]'' and ''[[minor chord|minor]] [[Triad (music)|triads]]'' and then the ''[[augmented triad|augmented]]'' and ''[[diminished triad|diminished]] [[Triad (music)|triads]]''. The descriptions ''major'', ''minor'', ''augmented'', and ''diminished'' are sometimes referred to collectively as chordal ''quality''. Chords are also commonly classed by their [[root (chord)|root]] note—so, for instance, the chord '''C''' major may be described as a triad of major quality built on the note '''C'''. Chords may also be classified by [[Inverted chord|inversion]], the order in which the notes are stacked.

A series of chords is called a [[chord progression]]. Although any chord may in principle be followed by any other chord, certain patterns of chords have been accepted as establishing [[Key (music)|key]] in [[Common practice harmony|common-practice harmony]]. To describe this, chords are numbered, using [[Roman numerals]] (upward from the key-note),{{sfn|Schoenberg|1983|loc=1–2}} per their [[diatonic function]]. Common ways of [[#Notation|notating or representing chords]]{{sfn|Benward and Saker|2003|loc=77}} in western music other than conventional [[staff notation]] include [[Roman numerals#Music theory|Roman numerals]], [[figured bass]] (much used in the [[Baroque music|Baroque era]]), [[chord letter]]s (sometimes used in modern [[musicology]]), and various systems of [[chord chart]]s typically found in the [[lead sheet]]s used in [[Chord names and symbols (popular music)|popular music]] to lay out the sequence of chords so that the musician may play accompaniment chords or improvise a solo.