CHORD

WHAT IS A CHORD?

A chord, in music, is any harmonic set of usually three or more notes that is heard as if sounding simultaneously. These need not actually be played together: arpeggios and broken chords (these involve the notes of the chord played one after the other, rather than at the same time) may, for many practical and theoretical purposes, constitute chords. Chords and sequences of chords are frequently used in modern Western, West African and Oceanian music, whereas they are absent from the music of many other parts of the world.

In tonal Western classical music, the most frequently encountered chords are triads, so called because they consist of three distinct notes: the root note, a third above the root and a fifth interval above the root. Further notes may be added to give tetrads such as seventh chords (the most commonly encountered example being the dominant seventh chord) and added tone chords, as well as extended chords and tone clusters. Triads commonly found in the Western classical tradition are major and minor chords, with augmented and diminished chords appearing less often. The descriptions major, minor, augmented, and diminished are referred to collectively as chordal quality. Chords are also commonly classified by their root note—for instance, a C major triad consists of the pitch classes C, E, and G. A chord retains its identity if the notes are stacked in a different way vertically; however, if a chord has a note other than the root note as the lowest note, the chord is said to be in an inversion (this is also called an "inverted chord"). While most chords have at least three notes, power chords have just two notes.

An ordered series of chords is called a chord progression. One example of a widely used chord progression in Western traditional music and blues is the 12 bar blues progression, the simplest versions of which include tonic, subdominant and dominant chords (this system of naming chords is described later in this section). Although any chord may in principle be followed by any other chord, certain patterns of chords are more common in Western music, and some pattern have been accepted as establishing the key (tonic note) in common-practice harmony–notably the movement between tonic and dominant chords. To describe this, Western music theory has developed the practice of numbering chords using Roman numerals which represent the number of diatonic steps up from the tonic note of the scale.

Common ways of notating or representing chords in Western music other than conventional staff notation include Roman numerals, figured bass, macro symbols (sometimes used in modern musicology), and chord charts. Each of these systems is more likely to appear in certain contexts: figured bass notation was used prominently in notation of Baroque music, macro symbols are used in modern musicology, and chord charts are typically found in the lead sheets used in popular music and jazz. The chords in a song or piece are also given names which refer to their function. The chord built on the first note of a major scale is called the tonic chord (colloquially called a "I" or "one" chord). The chord built on the fourth note of a major scale is called the subdominant chord (colloquially called a "IV" chord or "four" chord). The chord built on the fifth degree of the major scale is called the dominant chord (colloquially called a "V chord" or "five" chord). There are names for the chords built on every note of the major scale. Chords can be played on many instruments, including piano, pipe organ, guitar and mandolin. Chords can also be performed when multiple musicians play together in a musical ensemble or when multiple singers sing in a choir and they play or sing three or more notes at the same time.