Chord (music)
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- This article describes musical chords in traditional Western styles. For information on non-Western styles, consult the articles specific to those styles.
In music and music theory a chord (from Greek χορδή: gut, string) is two (Sadie 2001,[page # needed]) 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.
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[edit] History
The word chord comes from cord which is a Middle English shortening of accord. In the Middle Ages, Western harmony featured the perfect intervals of a fourth, a fifth, and an octave. In the 15th and 16th centuries, the major and minor triads (see below) became increasingly common, and were soon established as the default sonority for Western music. Four-note "seventh chords" were then widely adopted from the 17th century. The harmony of many contemporary popular Western genres continues to be founded in the use of triads and seventh chords, though far from universally. Notable exceptions include: modern jazz (especially circa 1960), in which chords often include at least five notes, with seven (and occasionally more) being quite common; and atonal or post-tonal contemporary classical music (including the music of some film scores), whose chords can be far more complex, rooted in such disparate harmonic philosophies that traditional terms such as triad are rarely useful.
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).
[edit] Constructing and naming chords
Every chord has certain characteristics, which include:
- the number of chromas used in constructing the chord (or the number of distinct pitch classes from which the chord takes its notes)
- the general type of intervals it contains: for example seconds, thirds, or fourths.
- its precise intervallic construction, sometimes called "chord quality": for example, if the chord is a triad, is the triad a major, minor, augmented or diminished?
- the scale degree of the root note
- whether the chord is inverted in register
[edit] Number of notes
One way of classifying chords is according to the number of distinct pitch classes used in their construction, a pitch class being identified by a degree of the scale (that is, a certain musical note, such as A, B, C, D, etc.) without regard to which octave it occurs in. Chords using three pitch classes are called triads. Chords using four notes are known as tetrads. Those using five are called pentads, and those using six are hexads. They are sometimes called trichords, tetrachords, pentachords and hexachords, however these terms more usually refer to contiguous pitch clases in some scale, usually spanning a perfect fourth, and not generally played simultaneously.
Theorists differ as to whether chords consist of at least three pitches. Otto Karolyi ([cite this quote], 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.)"
[edit] Type of interval
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.
[edit] Quality and triads
The quality of a triad is determined by the precise arrangement of its intervals. Tertian triads can be described as a series of three notes. The first element is called the root note of the chord, the second note is called the "third" of the chord, and the last note is called the "fifth" of the chord. These are described below:
| Chord name | Component intervals | Example | Chord symbol | |
|---|---|---|---|---|
| major triad | major third | perfect fifth | C-E-G | C, CM, Cma, Cmaj |
| 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 | <a href="/wiki/Diminished_fifth" class="mw-redirect" title=" | ||