Chord (music)

In Western music theory, a chord is a group[a] of notes played together for their harmonic consonance or dissonance.

Chords are the building blocks of harmony and form the harmonic foundation of a piece of music.

They provide the harmonic support and coloration that accompany melodies and contribute to the overall sound and mood of a musical composition.

[11] Hence, Andrew Surmani, for example, states, "When three or more notes are sounded together, the combination is called a chord.

[15] A simple example of two notes being interpreted as a chord is when the root and third are played but the fifth is omitted.

Jean-Jacques Nattiez explains that, "We can encounter 'pure chords' in a musical work", such as in 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 Claude Debussy's Première arabesque.

[9] In the medieval era, early Christian hymns featured organum (which used the simultaneous perfect intervals of a fourth, a fifth, and an octave[16]), with chord progressions and harmony - an incidental result of the emphasis on melodic lines during the medieval and then Renaissance (15th to 17th centuries).

[4] It was in the Baroque period that the accompaniment of melodies with chords was developed, as in figured bass,[18] and the familiar cadences (perfect authentic, etc.).

[23] Many contemporary popular Western genres continue to rely on simple diatonic harmony, though far from universally:[24] 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).

In organ registers, certain chords are activated by a single key so that playing a melody results in parallel voice leading.

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.

In some conventions (as in this and related articles) upper-case Roman numerals indicate major triads (e.g., I, IV, V) while lower-case Roman numerals indicate minor triads (e.g., I for a major chord and i for a minor chord, or using the major key, ii, iii and vi representing typical diatonic minor triads); other writers (e.g., Schoenberg) use upper case Roman numerals for both major and minor triads.

Figured bass is closely associated with chord-playing basso continuo accompaniment instruments, which include harpsichord, pipe organ and lute.

In the 2010s, some classical musicians who specialize in music from the Baroque era can still perform chords using figured bass notation; in many cases, however, the chord-playing performers read a fully notated accompaniment that has been prepared for the piece by the music publisher.

[29] In most genres of popular music, including jazz, pop, and rock, a chord name and the corresponding symbol are typically composed of one or more parts.

The basic function of chord symbols is to eliminate the need to write out sheet music.

The modern jazz player has extensive knowledge of the chordal functions and can mostly play music by reading the chord symbols only.

Sometimes the terms trichord, tetrachord, pentachord, and hexachord are used—though these more usually refer to the pitch classes of any scale, not generally played simultaneously.

The tonic of the scale may be indicated to the left (e.g., "F♯:") or may be understood from a key signature or other contextual clues.

Roman numeral analysis indicates the root of the chord as a scale degree within a particular major key as follows.

Where guitar chords are concerned, the term "inversion" is used slightly differently; to refer to stock fingering "shapes".

Harmonic semitones are an important part of major seventh chords, giving their sound a characteristic high tension, and making the harmonic semitone likely to move in certain stereotypical ways to the following chord.

Jazz voicings typically use the third, seventh, and then the extensions such as the ninth and thirteenth, and in some cases the eleventh.

[39] The other group is inverted chords in which the interval of a sixth appears above a bass note that is not the root.

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): The augmented sixth family of chords exhibits certain peculiarities.

Nowadays, this is mostly for academic study or analysis (see figured bass) but the Neapolitan sixth chord is an important example; a major triad with a flat supertonic scale degree as its root that is called a "sixth" because it is almost always found in first inversion.

The name suspended derives from an early polyphonic technique developed during the common practice period, in which a stepwise melodic progress to a harmonically stable note in any particular part was often momentarily delayed, or suspended, by extending the duration of the previous note.

The resulting unexpected dissonance could then be all the more satisfyingly resolved by the eventual appearance of the displaced note.

In modern lay usage, the term is restricted to the displacement of the third only, and the dissonant second or fourth no longer must be held over (prepared) from the previous chord.

Neither is it now obligatory for the displaced note to make an appearance at all, though in the majority of cases the conventional stepwise resolution to the third is still observed.