In music and music theory a chord (from Greek χορδή: gut, string) is a set of three or more different notes that sound simultaneously. Most often, in European-influenced music, chords are tertian sonorities that can be constructed as stacks of thirds relative to some underlying scale. Two-note combinations are typically referred to as dyads or intervals. A succession of chords is called a chord progression.
Chords are so well-established in Western music that sonorities of two pitches, or even monophonic melodies, are often interpreted by listeners (musicians and non-musicians alike) as "implying" chords. This psychoacoustic phenomenon occurs as a result of a lifetime of exposure to the conventional harmonies of music, with the result that the brain "supplies" the complete expected chord in its absence.
Composers can and do take advantage of this tendency to surprise the listener, by deliberately avoiding certain defining tones. For instance, a composition may be predominantly composed in the pentatonic minor scale, implying common Aeolian mode to the listener, before deliberately including a more uncommon tone in a melodic progression or chord, such as a major VI (signalling Dorian mode) or a flattened II (signalling Phrygian mode).
Every chord has certain characteristics, which include:
Theorists differ as to whether chords consist of at least three pitches. Otto Karolyi (p.63), disagrees, writing that, "two or more notes sounded simultaneously are known as a chord. The vertical combination of three sounds: fundamental note, third and fifth, gives us a chord known as a triad." In contrast, Andrew Surmani (2004, p.72), writes that, "when three or more notes are sounded together, the combination is called a chord," and George T. Jones explains (1994, p.43) "two tones sounding together are usually termed an interval, while three or mores tones are called a chord." According to Monath (1984, p.37) "A chord is a combination of three or more tones sounded simultaneously for which the distances (called intervals) between the tones are based on a particular formula. (Two notes sounded simultaneously are not considered to be chords and are simply called intervals.)"
Many chords can be arranged as a series whose elements are separated by intervals that are all roughly the same size. For example, a C major triad contains the notes C, E, and G. These notes can be arranged in the series C-E-G, in which the first interval (C-E) is a major third, while the second interval (E-G) is a minor third. Any chord that can be arranged as a series of (major or minor) thirds is called a tertian chord. A chord such as C-D-E is a series of seconds, containing a major second (C-D) and a minor second (D-E). Such chords are called secundal. The chord C-F-B, which consists of a perfect fourth C-F and an augmented fourth (tritone) F-B is called quartal. Most Western music uses tertian chords.
On closer examination, however, the terms "secundal", "tertian" and "quartal" can become ambiguous. The terms "second," "third," and "fourth" (and so on) are often understood relative to a scale, but it is not always clear which scale they refer to. For example, consider the pentatonic scale G-A-C-D-F. Relative to the pentatonic scale, the intervals G-C and C-F are "thirds," since there is one note between them. Relative to the chromatic scale, however, the intervals G-C and C-F are "fourths" since they are five semitones wide. For this reason the chord G-C-F might be described both as "tertian" and "quartal," depending on whether one is measuring intervals relative to the pentatonic or chromatic scales.
The use of accidentals complicates the picture. The chord B-E-A is notated as a series of diminished fourths (B-E) and (E-A). However, the chord is enharmonically equivalent to (and sonically indistinguishable from) C-E-G, which is a series of major thirds (C-E) and (E-G). Notationally, then, B-E-A is a "fourth chord," even though it sounds identical to the tertian chord C-E-G. In some circumstances it is useful to talk about how a chord is notated, while in others it is useful to talk about how it sounds. Terms such as "tertian" and "quartal" can be used in either sense, and it is important to be clear about which is intended.
|Chord name||Component intervals||Example||Chord symbol||Audio|
|major triad||major third||perfect fifth||C-E-G||C, CM, Cma, Cmaj, CΔ|
|minor triad||minor third||perfect fifth||C-E-G||Cm, Cmi, Cmin|
|augmented triad||major third||augmented fifth||C-E-G||C+, C+, Caug|
|diminished triad||minor third||diminished fifth||C-E-G||Cm(5), Cº, Cdim|
The major triad formed using the C note as the root would consist of C (the root note of the scale), E (the third note of the scale) and G (the fifth note of the scale). This triad is major because the interval from C to E is a major third.
Using the same scale (and thus, implicitly, the key of C major) a minor chord may be constructed using the D as the root note. This would be D (root), F (third note), A (fifth note).
Examination at the piano keyboard will reveal that there are four semitones between the root and third of the chord on C, but only 3 semitones between the root and third of the chord on D (while the outer notes are still a perfect fifth apart). Thus the C triad is major while the D triad is minor.
A triad can be constructed on any note of the C major scale. These will all be either minor or major, with the exception of the triad on B, the leading-tone (the last note of the scale before returning to a C, in this case), which is diminished. For more detail see the article on the mathematics of the Western music scale.
For example, since the first scale degree of the C major scale is the note C, a triad built on top of the note C would be called the one chord, which might be notated 1, I, or even C, in which case the assumption would be made that the key signature of the particular piece of music in question would indicate to the musician what function a C major triad was fulfilling, and that any special role of the chord outside of its normal diatonic function would be inferred from the context.
When taking any major (Ionian) scale and building a triad with a base in the scale, the second, third, and sixth intervals, when used as a root, will form a minor triad. The root, fourth, and fifth form a major triad, whereas the seventh will form a diminished triad. When in minor modes, building a triad upon the tonic, fourth and fifth degrees of the scale will result in a minor chord. Building upon scale degree two will result in a diminished chord, while building a triad upon scale degrees three, six and seven will yield major chords.
|Scale degree||tonic||supertonic||mediant||subdominant||dominant||submediant||leading tone/subtonic|
The scale to whose scale degrees the Roman numerals refer may be indicated to the left (e.g. F:), but may also be understood from the key signature or other contextual clues.
Unlike pop chord symbols, which are used as a guide to players, Roman numerals are used primarily as analytical tools, and so indications of inversions or added tones are sometimes omitted if they are not relevant to the analysis being performed.
The number of inversions that a chord can have is one fewer than the number of constituent notes. Triads, for example, (having three constituent notes) can have three positions, two of which are inversions:
Five common types of seventh chords have standard symbols. The chord quality indications are sometimes superscripted and sometimes not (e.g. Dm7, Dm7, and Dm7 are all identical). The last three chords are not used commonly except in jazz.
|Chord name||Component notes (chord and interval)||Chord symbol||Audio|
|major seventh||major triad||major seventh||CMaj7, CMA7, CM7, CΔ7, Cj7, C+7|
|dominant seventh||major triad||minor seventh||C7, C7, Cdom7|
|minor seventh||minor triad||minor seventh||Cm7, C−7, C−7|
|diminished seventh||diminished triad||diminished seventh||Co7, Cdim7|
|half-diminished seventh||diminished triad||minor seventh||Cø7, Cm75, C-7(5)|
|augmented major seventh||augmented triad||major seventh||C+(Maj7), C+MA7, CMaj7+5, CMaj75, C+j7, CΔ+7|
|augmented seventh||augmented triad||minor seventh||C+7, C7+, C7+5, C75|
|minor major seventh||minor triad||major seventh||Cm(Maj7), C−(j7), Cm7, C−Δ7, C−maj7|
When a dominant seventh chord (a major minor seventh in its most common function) is borrowed from another key, the Roman numeral corresponding with that key is shown after a slash. For example, V/V indicates the dominant of the dominant. In the key of C major, where the dominant (V) chord is G major, this secondary dominant is the chord on the fifth degree of the G major scale, i.e. D major. Note that while the chord built on D (ii) in the key of C major would normally be a minor chord, the V/V chord, also built on D, is major.
To add one note to a single triad, the equivalent simple intervals are used. Because an octave has seven notes, these are as follows:
|Chord name||Component notes (chord and interval)||Musical notation||Audio|
|Add nine||major triad||ninth||-||-||C2, Cadd9|
|Major 4th||major triad||perfect fourth||-||-||C4, Cadd11|
|Major sixth||major triad||sixth||-||-||C6|
|Dominant ninth||dominant seventh||major ninth||-||-||C9|
|Dominant eleventh|| dominant seventh |
the third is usually omitted
|major ninth||perfect eleventh||-||C11|
|Dominant thirteenth|| dominant seventh|
the eleventh is usually omitted
|major ninth||perfect eleventh||major thirteenth||C13|
Other extended chords follow the logic of the rules shown above.
Thus Maj9, Maj11 and Maj13 chords are the extended chords shown above with major sevenths rather than minor sevenths. Similarly, m9, m11 and m13 have minor thirds and minor sevenths.
Extended chords, composed of triads can also have variations. Thus madd9, m4 and m6 are minor triads with extended notes.
In Western music, the most common use of augmented sixth chords is to resolve to a dominant chord in root position (that is, a dominant triad with the root doubled to create the octave to which the augmented sixth chord resolves), or to a tonic chord in second inversion (a tonic triad with the fifth doubled for the same purpose). In this case, the tonic note of the key is included in the chord, sometimes along with an optional fourth note, to create one of the following (illustrated here in the key of C major):
The augmented sixth family of chords exhibits certain peculiarities. Since they are not triad-based, as are seventh chords and other sixth chords, they are not generally regarded as having roots (nor, therefore, inversions), although one re-voicing of the notes is common (with the namesake interval inverted so as to create a diminished third).
Accidentals are most often used in conjunction with dominant seventh chords. For example:
|Chord name||Component notes||Chord symbol||Audio|
|Seventh augmented fifth||dominant seventh||augmented fifth||C7+5, C75|
|Seventh flat nine||dominant seventh||minor ninth||C7-9, C79|
|Seventh sharp nine||dominant seventh||augmented ninth||C7+9, C79|
|Seventh augmented eleventh||dominant seventh||augmented eleventh||C7+11, C711|
|Seventh flat thirteenth||dominant seventh||minor thirteenth||C7-13, C713|
|Half-diminished seventh||minor seventh||diminished fifth||Cø, Cm75|
"Altered" dominant seventh chords (C7alt) have a flat ninth, a sharp ninth, a diminished fifth and an augmented fifth (see Levine's Jazz Theory). Some write this as C7+9, which assumes also the flat ninth, diminished fifth and augmented fifth (see Aebersold's Scale Syllabus).
When superscripted numerals are used, the different numbers may be listed horizontally (as shown), or vertically.
The name suspended derives from an early voice leading technique developed during the common practice period of composition, in which an anticipated stepwise melodic progression to a harmonically stable note in any particular part (voice) was often momentarily delayed or suspended simply by extending the duration of the previous note. The resulting unexpected dissonance could then be all the more satisfyingly resolved by the eventual appearance of the displaced note.
In modern usage, without regard to such considerations of voice leading, the term suspended is restricted to those chords involving the displacement of the third only, and the dissonant second or fourth no longer needs to be prepared from the previous chord. Neither is it now obligatory for the displaced note to make an appearance at all. However, in the majority of occurrences of suspended chords, the conventional stepwise resolution to the third is still observed.
Note that, in traditional music theory, the inclusion of the third in either the suspended second or suspended fourth chords negates the effect of suspension, and such chords are properly called added ninth and added eleventh chords rather than suspended chords.
A notable exception to this analysis of suspended chords occurs in jazz theory. In post-bop and modal jazz compositions and improvisations, suspended seventh chords are often used in nontraditional ways. In these contexts, they often do not function as V chords, and do not resolve the fourth to the third; the lack of resolution gives the chord an ambiguous, static quality. Indeed, the third is often played on top of a sus4 chord; in jazz theory, this doesn't negate the quality of the chord as a suspended chord. A good example is the jazz standard Maiden Voyage
If a chord is borrowed from the parallel key, this is usually indicated directly (e.g. IV (minor)) or explained in a footnote or accompanying text.If there is no mention of tonality upper case can be taken as the major and lower case as minor.
The tables in the linked subarticle include a column showing the pop chord symbols commonly used as an abbreviated notation using letters, numbers, and other symbols and usually written above the given lyrics or staff. Although these symbols are used occasionally in classical music as well, they are most common for lead sheets and fake books in jazz and other popular music.
Chords are commonly played in sequence, much as notes are played in sequence to form melodies. Chord sequences can be conceptualised either in a simplistic way, in which the root notes of the chords play simple melodies while tension is created and relieved by increasing and decreasing dissonance, or full attention can be paid to each note in every chord, in which case chord sequences can be regarded as multi-part harmony of unlimited complexity.
Since simultaneity is not a required feature of chords, there has been some academic discussion regarding the point at which a group of notes can be called a chord. Jean-Jacques Nattiez (1990, p.218) explains that, "we can encounter 'pure chords' in a musical work," such as in the "Promenade" of Modest Mussorgsky's Pictures at an Exhibition.
However, "often, we must go from a textual given to a more abstract representation of the chords being used," as in Claude Debussy's Première Arabesque. The chords on the second stave shown here are abstracted from the notes in the actual piece, shown on the first. "For a sound configuration to be recognized as a chord, it must have a certain duration."
Goldman (1965, p.26) elaborates: "the sense of harmonic relation, change, or effect depends on speed (or tempo) as well as on the relative duration of single notes or triadic units. Both absolute time (measurable length and speed) and relative time (proportion and division) must at all times be taken into account in harmonic thinking or analysis."
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