Guitar chord - WikiHQ

right|thumb|alt=Ry Cooder plays slide guitar|[[Ry Cooder plays slide guitar using an open tuning that allows major chords to be played by barring the strings anywhere along their length.]]

In music, a guitar chord is a set of notes played on a guitar. A chord's notes are often played simultaneously, but they can be played sequentially in an arpeggio. The implementation of guitar chords depends on the guitar tuning. Most guitars used in popular music have six strings with the "standard" tuning of the Spanish classical guitar, namely E–A–D–G–B–E' (from the lowest pitched string to the highest); in standard tuning, the intervals present among adjacent strings are perfect fourths except for the major third (G,B). Standard tuning requires four chord-shapes for the major triads.

There are separate chord-forms for chords having their root note on the third, fourth, fifth, and sixth strings. For a six-string guitar in standard tuning, it may be necessary to drop or omit one or more tones from the chord; this is typically the root or fifth. The layout of notes on the fretboard in standard tuning often forces guitarists to permute the tonal order of notes in a chord.

The playing of conventional chords is simplified by open tunings, which are especially popular in folk, blues guitar and non-Spanish classical guitar (such as English and Russian guitar). For example, the typical twelve-bar blues uses only three chords, each of which can be played (in every open tuning) by fretting six strings with one finger. Open tunings are used especially for steel guitar and slide guitar. Open tunings allow one-finger chords to be played with greater consonance than do other tunings, which use equal temperament, at the cost of increasing the dissonance in other chords.

The playing of (3 to 5 string) guitar chords is simplified by the class of alternative tunings called regular tunings, in which the musical intervals are the same for each pair of consecutive strings. Regular tunings include major-thirds tuning, all-fourths, and all-fifths tunings. For each regular tuning, chord patterns may be diagonally shifted down the fretboard, a property that simplifies beginners' learning of chords and that simplifies advanced players' improvisation. On the other hand, in regular tunings 6-string chords (in the keys of C, G, and D) are more difficult to play.

Conventionally, guitarists double notes in a chord to increase its volume, an important technique for players without amplification; doubling notes and changing the order of notes also changes the timbre of chords. It can make possible a "chord" which is composed of the all same note on different strings. Many chords can be played with the same notes in more than one place on the fretboard.

Musical fundamentals

The theory of guitar-chords respects harmonic conventions of Western music. Discussions of basic guitar-chords rely on fundamental concepts in music theory: the twelve notes of the octave, musical intervals, chords, and chord progressions.

Intervals

right|thumb|The chromatic circle lists the twelve notes of the octave, which differ by exactly one semitone.

thumb|upright=1.5|One-octave C major [[musical scale|scale ]]

thumb|Initial eight harmonics on C, namely (C,C,G,C,E,G,B,C)[[File:First eight harmonics vertical.mid|thumb|Play simultaneously]]

The octave consists of twelve notes.

Its natural notes constitute the C major scale, (C, D, E, F, G, A, B, and C).

The intervals between the notes of a chromatic scale are listed in a table, in which only the emboldened intervals are discussed in this article's section on fundamental chords; those intervals and other seventh-intervals are discussed in the section on intermediate chords. The unison and octave intervals have perfect consonance. Octave intervals were popularized by the jazz playing of Wes Montgomery. The perfect-fifth interval is highly consonant, which means that the successive playing of the two notes from the perfect fifth sounds harmonious.

A semitone is the distance between two adjacent notes on the chromatic circle, which displays the twelve notes of an octave.

{|class="wikitable"

|+Intervals

! Number of<br/>semitones|| Minor, major, or perfect<br />intervals || Audio || Harmoniousness

| 0 || Perfect unison || ||Open consonance

| 1 || Minor second || ||Sharp dissonance

| 2 || Major second || ||Mild dissonance

| 3 || Minor third || ||Soft consonance

| 4 || Major third || ||Soft consonance

| 5 || Perfect fourth || ||Ambivalence

| 6 || Augmented fourth || ||Ambiguous

| 7 || Perfect fifth || ||Open consonance

| 8 || Minor sixth || ||Soft consonance

| 9 || Major sixth || ||Soft consonance

| 10 || Minor seventh || ||Mild dissonance

| 11 || Major seventh || ||Sharp dissonance

| 12 || Octave || ||Open consonance

As indicated by their having been emboldened in the table, a handful of intervals—thirds (minor and major), perfect fifths, and minor sevenths—are used in the following discussion of fundamental guitar-chords.

As already stated, the perfect-fifths (P5) interval is the most harmonious, after the unison and octave intervals. An explanation of human perception of harmony relates the mechanics of a vibrating string to the musical acoustics of sound waves using the harmonic analysis of Fourier series. When a string is struck with a finger or pick (plectrum), it vibrates according to its harmonic series. When an open-note C-string is struck, its harmonic series begins with the terms (C,C,G,C,E,G,B,C). The root note is associated with a sequence of intervals, beginning with the unison interval (C,C), the octave interval (C,C), the perfect fifth (C,G), the perfect fourth (G,C), and the major third (C,E). In particular, this sequence of intervals contains the thirds of the C-major chord {(C,E),(E,G)}.

Perfect fifths

The perfect-fifth interval is featured in guitar playing and in sequences of chords. The sequence of fifth intervals built on the C-major scale is used in the construction of triads, which is discussed below.

Cycle of fifths

Concatenating the perfect fifths <big>(</big>(F,C), (C,G), (G,D), (D,A), (A,E), (E,B),...<big>)</big> yields the sequence of fifths (F,C,G,D,A,E,B,...); this sequence of fifths displays all the notes of the octave. This sequence of fifths shall be used in the discussions of chord progressions, below.

Power chord

thumb|right|upright=0.85|The Who's Peter Townshend often used a theatrical "windmill" strum to play "power chords"—a root, fifth, and octave.

The perfect-fifth interval is called a power chord by guitarists, who play them especially in blues and rock music. The Who's guitarist, Peter Townshend, performed power chords with a theatrical windmill-strum. are discussed. These basic chords arise in chord-triples that are conventional in Western music, triples that are called three-chord progressions. After each type of chord is introduced, its role in three-chord progressions is noted.

Intermediate discussions of chords derive both chords and their progressions simultaneously from the harmonization of scales. The basic guitar-chords can be constructed by "stacking thirds", that is, by concatenating two or three third-intervals, where all of the lowest notes come from the scale.

Triads

Major

Both major and minor chords are examples of musical triads, which contain three distinct notes. Triads are often introduced as an ordered triplet:

the root;
the third, which is above the root by either a major third (for a major chord) or a minor third (for a minor chord);
the fifth, which is a perfect fifth above the root; consequently, the fifth is a third above the third—either a minor third above a major third or a major third above a minor third. The major triad has a root, a major third, and a fifth. (The major chord's major-third interval is replaced by a minor-third interval in the minor chord, which shall be discussed in the next subsection.)

{| class="wikitable"

|+ Major chords

!bgcolor=#dddddd|Chord

!bgcolor=#dddddd|Root

!bgcolor=#dddddd|Major third

!bgcolor=#dddddd|Fifth