In music and music theory, a chord (from the middle English cord, short for accord) is three or more different notes or pitches sounding simultaneously, or nearly simultaneously, over a period of time. For example, if you simultaneously play any three (or more) keys of a piano, you have just played a chord. Likewise, if you simultaneously play three or more strings of a guitar, you have just played a chord on the guitar. Every chord is given a specific name, based on the notes that constitute the chord and the distances, or intervals, between them.
Originally, a chord simply meant the sounding together of different tones, the resultant of these tones. Broadly, any combination of three or more notes is a chord, although during the common practice period in western music and most popular music some combinations were given more prominence than others. Thus in common usage a chord is only those groups of three notes which are tonal or have diatonic functionality. Chords being directly perceived units, sonorities of two pitches are often interpreted as fragments of three- or four-note chords.
A chord is then also only the harmonic function of the group of three notes, and it is unnecessary to have all three notes form a simultaneity. Less than three notes may and often do function, in context, as a simultaneity of all notes of chord. One example is a power chord, another is a broken chord or arpeggio, where each note in a chord is sounded one after the other. One of the most familiar broken chord figures is Alberti bass. See accompaniment.
Although, as Jean-Jacques Nattiez (1990, p.218) explains, "we can encounter 'pure chords' in a musical work," such as in the following example from the "Promenade" of Modest Mussorgsky's Pictures at an Exhibition:
But "often, we must go from a textual given to a more abstract representation of the chords being used," as in the following example where the chords on the second stave are abstracted from the actual notes written 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."
Music is said to be chord-based when the melody is determined by the chords and not by melodic concerns such as modal frames.
Nonchord tones and dissonance
A nonchord tone is a dissonant or unstable tone which is not a part of the chord that is currently playing and in most cases quickly resolves to a chord tone.
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.
Satie Sarabande 3 chord sequence.ogg to an example of a chord sequence from Erik Satie's Sarabande no. 3.
Harmonic analysis and construction
Chords are named for how many notes they contain, more commonly for what type of intervals they are constructed from, and by the root note and bass note.
The easiest way to name a chord, or limit its construction, is according to the number of notes included. The simplest and possibly most frequently used chords are trichords, meaning they have three ("tri") notes (before any doubling of notes, that is), four notes being a tetrachord, six a hexachord, etc.
It is more informative to label a chord based on what type of intervals it contains, rather than how many notes, because no matter how many notes a similar interval apart you stack on top of each other, the chord still retains a characteristic sound. The chords most traditionally used in Western music are those with notes fundamentally a third apart (that is, before any inversions and doublings, discussed below), called tertian chords. Chords constructed from seconds are secundal, and from fourths are quartal.
Chords are also distinguished and notated by the scale degree, pitch, or note of their root and bass, although there are many different conventions for indicating the quality of the chord, and the inversion of the chord (determined by which note of the chord serves as the bass note); see Inverted Triads below). 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.
Chords are labelled with chord symbols.
The most commonly used chords in Western music, triads are the basis of diatonic harmony, and are tertian trichords. That is, they are composed of three notes: a root note, a note which is a third above the root, and a note which is a third above that note, and therefore a fifth above the root.
Each note has a function within the chord: the note the chord is built on is called the root of the chord, the second note (a third above the root) is called the third of the chord, and the third note (a third above the second note) is called the fifth of the chord. This is true of all triads, regardless of key, inversion, or quality. For example, in an F triad, F is always the root, A (sharp, natural, or flat) is always the third, and C (sharp, natural, or flat) is always the fifth.
For another example, consider an octave of the C major scale, consisting of the notes C D E F G A B C:
Fig 1. The C major scale
The 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).
Fig 2. C, E and G - The C major triad
Using the same scale (and thus, implicitly, the key of C major) a chord may be constructed using the D as the root note. This would be D (root), F (third), A (fifth).
It should be immediately apparent on hearing these two chords that they have a different quality to them: one which does not stem merely from the difference in pitch between their roots C and D. 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).
This triad on C is therefore called a major triad, or major chord, since the interval from C to E is a major third. A minor chord, such as the triad on D, has a smaller interval from root to third called a minor third, and the chord is D 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. See also Mathematics of the Western music scale.
Types of triads
As well as major and minor, there can also be augmented and diminished triads. These four terms describe the quality of a chord. For instance a triad built on top of a root D in the key of C would be said to be minor or have a minor quality.
Augmented triads are composed of the root, a note a major third from the root, but then a note an augmented fifth from the root (unlike the major and minor triads); or equivalently, a major third on top of a major third (same as a major triad, except the top note has been raised by a semitone). Diminished triads have the root, a note a minor third from the root, but then a note a diminished fifth from the root, or a minor third on a minor third (same as a minor triad, except the top note has been lowered by a semitone.) These rules summarise the type of triads encountered so far:
Triads are said to be inverted when a note other than the root serves as the bass note (that is, it is the lowest note sounded). There are three positions that triads can have, two of which are inversions:
- Root position is when the chord is as described above: in ascending thirds with its root note in the bass.
- First inversion is when the third of the chord is in the bass, with the fifth of the chord next above, and the root highest.
- Second inversion is when the fifth of the chord in the bass, with the root next above, and the third of the chord highest.
For one traditional system of notation for inverted chords, see figured bass. Most Western music of any sophistication makes extensive use of inversion, since without it the harmonic resources available would be severely limited.
Cmaj min inversions.ogg to some triads: the first three chords played are C major root position, first inversion, second inversion; then C minor root position, first inversion, second inversion.
- Main article: Seventh chord.
Seventh chords may be thought of as the next natural step in composing tertian chords. Seventh chords are constructed by adding a fourth note to a triad, at the interval of a third above the fifth of the chord. This creates the interval of a seventh above the root of the chord. There are various types of seventh chords depending on the quality of the original chord and the quality of the seventh added.
- Main article: Extended chord.
Extended chords are tertian chords (built from thirds) or triads with notes extended, or added, beyond the seventh. Thus ninth, eleventh, and thirteenth chords are extended chords. After the thirteenth, any notes added in thirds duplicate notes elsewhere in the chord, so there are no fifteenth chords, seventeenth chords, and so on.
Augmented sixth chords
- Main article: Augmented sixth chord.
An augmented sixth chord is a chord which contains two notes which are separated by an augmented sixth (or, by inversion, a diminished third - though this inversion is rare in compositional practice). The augmented sixth is generally used as a dissonant interval which resolves by both notes moving outward to an octave.
In Western music, the most common use of these 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):
- Italian Augmented Sixth Chord: A flat, C, F sharp
- French Augmented Sixth Chord: A flat, C, D, F sharp
- German Augmented Sixth Chord: A flat, C, E flat, F sharp
Added tone chords
- Main article: Added tone chord.
An added tone chord is a traditional chord with an extra "added" note, such as the commonly added sixth (above the root). This includes chords with an added second (ninth) or fourth (thirteenth), or a combination of the three. These chords do not include "intervening" thirds as in an extended chord.
- Main article: Sustained chord.
A sustained chord, or "sus chord" (also suspended chord), is a chord where the second or most often the fourth is played with or replaces the third. For instance, Csus4 is C, F, and G. These chords are called "sustained" because you typically arrive at them when you perform a V7-I progression but don't resolve the seventh of the V7. This is similar to a suspension, where the harmony shifts from one chord to another, but one or more notes of the first chord are held over into the second. However in a sustained chord the note may never resolve as is required of a suspension. In jazz, sus chords are usually played as a major triad with the second in the bass, e.g. a major C with a D bass is a Dsus7.
- Main article: Borrowed chord.
Borrowed chords are chords borrowed from the parallel minor or major. If the root of the borrowed chord is not in the original key, then they are named by the accidental. For instance, in major, a chord built on the parallel minor's sixth degree is a "flat six chord", written bVI. Borrowed chords are an example of mode mixture.
Neapolitan sixth chord
The Neapolitan sixth chord is a major triad with the lowered supertonic scale degree as its root. The chord is referred to as a "sixth" because it is almost always found in first inversion (first inversions being traditionally named like this, from their characteristic interval of a sixth from the bass). Though a technically accurate roman numeral analysis would be bII6, it is generally labelled N6. In C major, the chord is spelled (assuming root position) D flat, F, A flat.
Because it uses lowered altered tones, this chord is often grouped with the borrowed chords. However, the chord is not borrowed from the parallel major or minor, and may appear in both major and minor keys.
Other types of chords
"Power chords" consist of perfect fifths and fourths and may be considered triads which lack the third and thus double the root or fifth to create a third note. The lack of the third makes their quality ambiguous. Popularized by heavy metal music they are used extensively in many kinds of rock music, especially (see below). Polychords are two or more chords superimposed on top of one another. See also altered chord and Tristan chord.
Chords in popular music
Most current popular songs are based on three chord or four chord progressions, i.e. songs which only contain three or four chords, as a harmonic formulae on top of which the rest of the song is constructed. In rock, The rhythm guitarist plays these chords. Played well, the chord progression should be harder for the untrained ear to separate out the chords from the rest of the song, quite opposite to the lead melody, which has the listener's total conscious attention. The listener is not aware, that without the chords (along with the bass guitarist and the drums and percussion), there would be no melody, since the melody uses the chords as a backbone around which to structure itself.
Rhythm chords can also be played by keyboards. Due to the nature of modern synthesizers, there can be a variety of chord types, such as the long sustained chords and short chords and very short chords. These different types of chords are used to produce different types of emotional responses in the listener, and to help the main melody (along with the lyrics), deliver its message.
One of the reasons that listeners usually only remember the melody and not the chord progressions of a song (apart from the fact that the words of the song are sung to its melody) is that the chords comprise two or more simultaneous notes rather than one as in a melody. Often in rock the guitar sound is distorted so that more harmonics are heard resulting in a more complex sound.
- Dahlhaus, Carl. Gjerdingen, Robert O. trans. (1990). Studies in the Origin of Harmonic Tonality, p.67. Princeton University Press. ISBN 0691091358.
- Nattiez, Jean-Jacques (1990). Music and Discourse: Toward a Semiology of Music (Musicologie générale et sémiologue, 1987). Translated by Carolyn Abbate (1990). ISBN 0691027145.