Music Theory/Chords
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This is a basic introduction to chords. There is also a complete chord reference.
It is difficult to define what a chord is. Many people define it as several notes played simultaneously. This definition, while not entirely inaccurate, is very misleading. It is possible to play music involving chords on the flute, trumpet, or a lone human voice, all three being instruments capable of playing only one sound at a time. For our purposes, we will define a chord as the basic element of harmony. Before we can explain further, however, we must provide an example of chords.
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[edit] Triads
The triad is a class of chords, specifically three-note chords formed by this formula: 1-3-5 or root, third, fifth. In this example they are constructed of two consecutive thirds.
There are four kinds:
| Root | 3rd | 5th | |
|---|---|---|---|
| Major | 1 | 3 | 5 |
| Minor | 1 | ♭3 | 5 |
| Augmented | 1 | 3 | #5 |
| Diminished | 1 | ♭3 | ♭5 |
| ♭=flat/lowered; #=sharp/raised | |||
The major is very consonant; the minor is a bit less so but still consonant for most purposes. The augmented is very dissonant and the diminished is extremely dissonant as it contains a tritone (augmented fourth or, in this case, diminished fifth).
The major and minor triads may have their fifth omitted, although this is uncommon. If the third of a major or minor chord is omitted, the result is a fifth chord, which is often called a power chord when played on an overdriven guitar.
[edit] Triads and Inversions
If we look at a C major triad or three-voice chord it is based on combining a root voice (C) with two other voices at slightly different intervals of a third (E, a major third from C and G, a minor third from E). If we compare the key of C major to the C major chord using the names do, re, mi, fa, so, la, si, to represent the scale degrees 1, 2, 3, 4, 5, 6, 7, the C major chord is constructed from the notes do, mi, and so. This same relationship is true for all major triads in all corresponding major keys.
| Note | Degree | Name |
|---|---|---|
| C | 1 | do |
| D | 2 | re |
| E | 3 | mi |
| F | 4 | fa |
| G | 5 | so |
If we juxtapose these three notes (the root, major third and perfect fifth) they can be structured or 'voiced', C-E-G, E-G-C or G-C-E. No matter what order the three notes (called voices) are in they still create a C major chord. It does not matter if the voices are the singers in a choir or the instruments of an orchestra, if the notes are all either C, E, or G we simply have a gigantic sounding C chord.
The two consecutive intervals produced by these voicings would be:
- C E G = major third, minor third (root pos'n),
- E G C = minor third, perfect fourth (1st inv.),
- G C E = perfect fourth, major third (second inv.).
If the root (C) is on the bottom this voicing is called root position. If the third (E) is on the bottom it is called first inversion. If the fifth (G) is on the bottom this voicing of the triad is called second inversion.
Since there are only three possible voicings of a triad it is relatively easy to hear them in that they are a common feature of the past two centuries of traditional harmonic structures in Western music. The use of the exponentially more complex voicings arising from 4-voice, 5-voice and larger chords is more challenging. Some 4-voice chords are used in traditional, 'classical' and church music but others such as the diminished seventh were strictly forbidden in early sacred music as they contained the tritone interval; the mathematical halfway point in the octave which allegedly sounded Satanic. Other 4-voice chords were not used in symphonic and 'classical' music until the French Impressionist era and in modern jazz. All triads and 4-voice chords are built within the octave, or eight-note scale which encompasses the do-re-mi-fa-sol-la-ti-do of the major scale, for instance, or the scale steps 1-2-3-4-5-6-7-8; eight being the octave where the pattern starts over again.
All triadic and therefore, common, chords can be constructed the same way : using the 1 3 5 formula. Take the C scale, for instance :
| Degree 1 2 3 4 5 |
Chord Name |
1-3-5 Triad |
Rel. Name |
|---|---|---|---|
| C D E F G | C Major | C E G | I |
| D E F G A | D Minor | D F A | iim |
| E F G A B | E Minor | E G B | iiim |
| F G A B C | F Major | F A C | IV |
| G A B C D | G Major | G B D | V |
| A B C D E | A Minor | A C E | vim |
| B C D E F | B Diminished | B D F | viidim |
This works for any scale, and whether the chord formed is minor or major depends on the scale: the I, IV, V chords are major, and the rest are minor, with the seventh being diminished.
[edit] Some Four-Voice Chords
| Name | Voices |
|---|---|
| Dominant Seventh | 1 3 5 ♭7 |
| Major Seventh | 1 3 5 7 |
| Minor Seventh | 1 ♭3 5 ♭7 |
| Minor Sixth | 1♭3 5 6 |
| Half-Diminished Seventh | 1 ♭3 ♭5 ♭7 |
| Diminished Seventh | 1 ♭3 ♭5 ♭♭7 |
[edit] Intervals
All chords are made up of interlocking or overlapping intervals. An interval may be defined as the distance between two notes. The names of the chords are derived from the intervals that they are built from. In order of smallest to largest the ascending intervals (and distance in semitones) within the octave from a middle C would be as follows:
| Interval | Note | Semitones |
|---|---|---|
| Minor 2nd | D♭ | 1 |
| Major 2nd | D | 2 |
| Minor 3rd | E♭ | 3 |
| Major 3rd | E | 4 |
| Perfect 4th | F | 5 |
| Augmented 4th Diminished 5th |
F# G♭ |
6¹² |
| Perfect 5th | G | 7 |
| Augmented 5th Minor 6th |
G# A♭ |
8¹ |
| Major 6th | A | 9 |
| Minor 7th | B♭ | 10 |
| Major 7th | B | 11 |
| Octave (8th) | C | 12 |
| 1. Shaded interval pairs are enharmonic; one interval with two names. 2. The Tritone is six semitones. |
||
The dreaded tritone, six semitones up from the root (and six down from the octave), is harmonically bewildering, being neither fish nor fowl, exactly halfway from nowhere; one interval with two names (enharmonic in 12-tone equal temperament), the augmented 4th and the diminished 5th. Likewise, the enharmonic augmented 5th and minor 6th are eight semitones up from the root.
By observing that 2nds, 3rds, 6ths and 7ths are always either major or minor and 4ths and 5ths are always perfect, augmented (raised) or diminished (lowered) it becomes evident that major chords have a major 3rd, minor chords have a minor third, et cetera. By altering or manipulating these intervals by raising or lowering the third, fifth, seventh, and so on, all of the possible chords can be produced.
Some examples:
| Voices | Name |
|---|---|
| 1 3 5 | Major |
| 1 ♭3 5 | Minor |
| 1 ♭3 ♭5 | Diminished |
| 1 3 #5 | Augmented |
| 1 3 5 7 | Major 7th |
| 1 3 5 ♭7 | Dominant 7th |
| 1 ♭3 5 6 | Minor 6th |
| 1 ♭3 5 7 | Minor/Major 7th |
| 1 ♭3 5 ♭7 | Minor 7th |
| 1 ♭3 ♭5 ♭7 | Minor 7th b5 |
| 1 ♭3 ♭5 ♭♭7(6) | Diminished 7th |
| 1 3 #5 7 | Major 7th +5 |
| 1 3 #5 ♭7 | Dominant 7th +5 |
[edit] Applying chords
The easiest way to apply a triad, or indeed any chord, is to pick one on a polyphonic instrument (such as a piano) and play its three notes simultaneously. This is often how chords occur in actual music: an instrument plays all the notes in the chord at the same time. However, there are other possibilities. The simplest is to arpeggiate the chord, that is, to play its notes one at a time in any order, especially in a ascending or descending order. Often a melody can be written around the chord, using notes in the chord as well as a few other nearby notes in the chord's scale. When this is done while there is no accompaniment actually playing a chord, the chord is implied.
[edit] Seventh chords
Triads are often extended with some form of the seventh to form a seventh chord. When a chord is referred to as simply a seventh chord, usually the dominant seventh is meant, which is a major triad with a minor seventh, for instance, C-E-G-B♭. It is called the dominant seventh because the V chord, or "dominant chord" in the Latin naming system, is the only chord in the major scale that can naturally contain a minor seventh. Because all sevenths are dissonant intervals, any seventh chord is dissonant, in other words, a seventh chord is more tense than a major or minor chord. However, a few styles of music, such as jazz, make heavy use of seventh chords and may treat them as rather consonant.
[edit] Other chords
Some chords are defined by the relation to the key rather than by any inherent characteristics. The Neapolitan chord, for example, is an ordinary major chord, but its root is the lowered supertonic of the corresponding key, so the the Neapolitan of C major is a D♭ major chord. Additionally, the Neapolitan is usually found in first inversion. A borrowed chord is one from the parallel major or minor key. In C major, the parallel key is C minor and borrowed chords include E♭ major, B♭ major, and F minor.
