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. 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.

The triad

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.

Related Topics:
Triad - Diatonic - Harmony - Root - Third - Fifth

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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:

Related Topics:
Octave - Major scale

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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.

Related Topics:
Major chord - Major third - Minor chord - Minor third

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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.

Related Topics:
Leading-tone - 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.

Related Topics:
Augmented - Diminished

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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

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.
• 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.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~