Chord music: Encyclopedia - Chord music

Chord (music)

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. On a piano this can be done by playing any three (or more) keys; on a guitar it is done by playing three or more strings. 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. As a result, in common usage a chord is only those groups of three notes which are tonal or have diatonic functionality. Since chords are directly perceived units, sonorities of two pitches are often interpreted as fragments of three- or four-note chords.

Music is said to be chord-based when the melody is determined by the chords and not by melodic concerns such as modal frames.

Chord music - Simultaneity

A chord is only the harmonic function of a group of notes, and it is unnecessary for all the notes to be played together (called forming a simultaneity). For example, broken chords and arpeggios are ways of playing notes in succession so that they form chords. One of the most familiar broken chord figures is Alberti bass.

Since simultaneity is not a required feature of chords, there has been some academic dicussion 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 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 Premiere Arabesque 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."

Chord music - Harmonic analysis and construction

Chords are named after the type of intervals they are constructed from or sometimes after the number of notes they contain. They are often distinguished 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.

Chord music - Triads

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 next note (a third above the root) is called the third of the chord, and the next note (a third above, again) 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.

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).

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 below, and the article on the Mathematics of the Western music scale.

Chord music - Inverted triads

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, creating an interval of a fifth, and a third (i.e. the tonic root position is marked, "I" in a figured 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, creating an interval of a sixth and a third (this is marked as, "I6".).

• Second inversion is when the fifth of the chord in the bass, with the root next above, and the third of the chord highest, forming an interval of a sixth, and a fourth (This is marked "I6/4"). Second inversion is the most unstable chord position.

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. For example, a I6/4 (second inversion of the tonic) often had cadential function in early western music since scale degree 5 is in the bass.

Listen 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.

Chord music - Chord quality

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:

• Major triad (M): root, major 3rd, perfect 5th
• Minor triad (m): root, minor 3rd, perfect 5th
• Augmented triad (A): root, major 3rd, augmented 5th
• Diminished triad (d): root, minor 3rd, diminished 5th

Chord music - Seventh chords

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.

Chord music - Extended chords

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.

Chord music - Augmented sixth chords

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

Chord music - Added tone chords

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 (eleventh), or a combination of the three. These chords do not include "intervening" thirds as in an extended chord.

Chord music - Sustained chords

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.

Chord music - Borrowed chords

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.

Chord music - 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.

Chord music - Power chords

Power chords are simple harmonies, in that they do not consist of three or more different kinds of notes, but rather two kinds. They consist of perfect fifths and fourths and lack the third scale note. Often, players double the root or fifth to create a third note, but not a third kind of note. The lack of the third scale note makes their quality ambiguous, which in layman's terms means that it is not clear whether they are major or minor in their flavor. This is due to the fact that the major or minor quality of a chord is directly produced by the third or flatted third scale note. Popularized by heavy metal music they are used extensively in many kinds of rock music.

Chord music - Other types of chord

Polychords are two or more chords superimposed on top of one another. See also altered chord, secundal chord, Quartal and quintal harmony and Tristan chord.

Chord music - Chord sequences

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.

Listen to an example of a chord sequence from Erik Satie's Sarabande no. 3.

Chord music - 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.

See also

• Block chord
• Mu major chord

Adapted from the Wikipedia article "Chord music", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki