Chord (music)
In music, a chord is a group of two or more notes played simultaneously, typically consisting of a root note, a third, and a fifth.[a] Chords are the building blocks of harmony and form the harmonic foundation of a piece of music. They can be major, minor, diminished, augmented, or extended, depending on the intervals between the notes and their arrangement. Chords provide the harmonic support and coloration that accompany melodies and contribute to the overall sound and mood of a musical composition. For many practical and theoretical purposes, arpeggios and other types of broken chords (in which the chord tones are not sounded simultaneously) may also be considered as chords in the right musical context.
This article is about pitch simultaneity and harmony in music. For other uses, see Chord (disambiguation).
In tonal Western classical music (music with a tonic key or "home key"), the most frequently encountered chords are triads, so called because they consist of three distinct notes: the root note, and intervals of a third and a fifth above the root note. Chords with more than three notes include added tone chords, extended chords and tone clusters, which are used in contemporary classical music, jazz and almost any other genre.
A series of chords is called a chord progression.[1] One example of a widely used chord progression in Western traditional music and blues is the 12 bar blues progression. Although any chord may in principle be followed by any other chord, certain patterns of chords are more common in Western music, and some patterns have been accepted as establishing the key (tonic note) in common-practice harmony—notably the resolution of a dominant chord to a tonic chord. To describe this, Western music theory has developed the practice of numbering chords using Roman numerals[2] to represent the number of diatonic steps up from the tonic note of the scale.
Common ways of notating or representing chords[3] in Western music (other than conventional staff notation) include Roman numerals, the Nashville Number System, figured bass, chord letters (sometimes used in modern musicology), and chord charts.
History[edit]
In the medieval era, early Christian hymns featured organum (which used the simultaneous perfect intervals of a fourth, a fifth, and an octave[15]), with chord progressions and harmony - an incidental result of the emphasis on melodic lines during the medieval and then Renaissance (15th to 17th centuries).[16][17]
The Baroque period, the 17th and 18th centuries, began to feature the major and minor scale based tonal system and harmony, including chord progressions and circle progressions.[3] It was in the Baroque period that the accompaniment of melodies with chords was developed, as in figured bass,[17] and the familiar cadences (perfect authentic, etc.).[18] In the Renaissance, certain dissonant sonorities that suggest the dominant seventh occurred with frequency.[19] In the Baroque period, the dominant seventh proper was introduced and was in constant use in the Classical and Romantic periods.[19] The leading-tone seventh appeared in the Baroque period and remains in use.[20] Composers began to use nondominant seventh chords in the Baroque period. They became frequent in the Classical period, gave way to altered dominants in the Romantic period, and underwent a resurgence in the Post-Romantic and Impressionistic period.[21]
The Romantic period, the 19th century, featured increased chromaticism.[3] Composers began to use secondary dominants in the Baroque, and they became common in the Romantic period.[22] Many contemporary popular Western genres continue to rely on simple diatonic harmony, though far from universally:[23] notable exceptions include the music of film scores, which often use chromatic, atonal or post-tonal harmony, and modern jazz (especially c. 1960), in which chords may include up to seven notes (and occasionally more).[24] When referring to chords that do not function as harmony, such as in atonal music, the term "sonority" is often used specifically to avoid any tonal implications of the word "chord".
Chords are also used for timbre effects. In organ registers, certain chords are activated by a single key so that playing a melody results in parallel voice leading. These voices, losing independence, are fused into one with a new timbre. The same effect is also used in synthesizers and orchestral arrangements; for instance, in Ravel’s Bolero #5 the parallel parts of flutes, horn and celesta, being tuned as a chord, resemble the sound of an electric organ.[25][26]
