Chords provide strong harmonic foundation for melody. Although a chord may have as little as two notes, the most common chords are that of the three note variety, the triad. From this basis, extra notes are added in a sequence to create four, five and six note chords.
Chords can be constructed from any degree of a given scale. However, the most pivotal chords are those built from the tonic (first degree) and dominant (fifth degree). The tonic chord is important as it is often used at the beginning and the end of a harmony.
The dominant seventh chord is a unique four note chord. The dominant 7th, abbreviated to V7, can only be built upon the fifth degree. This provides a strong direction for the melody that it supports.
Dominant Seventh Chords
The dominant degree of a scale is the fifth degree. Constructing a four note chord upon the fifth degree will produce a dominant seventh chord. Using the C major scale as an example, the four note chord built from the 5th degree is G7.
G7 Chord Construction
When constructing a V7, this chord can be thought of as three intervals stacked in thirds. To create a V7 chord, stack a minor third on top of a major triad.
G7 Chord Stack
Naming Dominant Seventh Chords
Chords are mostly classified by the root or starting note. For example: C major triad is considered a three note chord with major quality built from the root of the C major scale. The dominant seventh chord is so named as its starting note is the dominant degree of the scale. As can be seen in the diagram above, in C major this chord is G7.
When referencing either scale degrees or chords, roman numeral are often used. For example, chord IV of C major is F major triad, F - A - C.
When referencing the dominant seventh chord, the roman numeral V is used to indicate a chord built from the fifth degree. That is, the root of the V7 is the fifth scale degree.
When correctly naming a V7 chord, the letter name of the chord is followed by the numeral 7. For example, the chord G- B - D - F is named G7. G - F is an interval of a minor seventh, hence the 7 in the chord name.
Harmonic function defines the relationship between chords of a given key.
Major triads are chords built upon the 1st (tonic), 4th (subdominant) and 5th (dominant) degrees of a major scale. Interestingly, melodies within a given key can be harmonized using only chords from the tonic, dominant and subdominant, as these chords contain every note of the scale. These three chords are referred to as primary triads.
These triads originate from the first, fourth, and fifth degrees of a major scale, and are often referred to as chords one, four and five. Roman numerals are used to indicate this. For example:
|C Major Scale|
|Chord I||Chord IV||Chord V|
The purpose of the tonic, chord I, is to act as the starting point, or grounding for the tonal system in which harmonic relationships are based. This tonal system is referred to as the
The subdominant and dominant, chords IV and V respectively, help define the tonal centre.
Chords IV and V provoke tonal tension that is resolved by resting on the chord I, the tonic. Scales degrees 4 and 7 of the major scale are considered tendency tones. These tones have a tendency to pull the harmony towards a resolution.
In C major, chord IV, F-A-C, contains the first tendency tone. F is the fourth degree of the scale, and the F naturally resolve a half-step down to E, the third of chord I, C-E-G.
Chord V, G-B-D, contains the seventh degree of the scale, B. The B, being the leading note, naturally resolves a half-step up to C, the tonic of chord I, C-E-G.
Tendency tones are notes within a melody or harmony that require resolution. In western culture the major scale is common place. For an example of tendency tones, sing the major scale as you would in solfege:
Sing this scale again, but this time, pause on the seventh degree:
The seventh degree, Ti, is pulled towards the revolution, the Do. Ti is a tendency tone in this effect.
The pull of the dominant seventh chord to resolve to the tonic is unmistakably strong. The reason for this is that the dominant seventh chord contains both tendency tones. For example:
|G7||G-B-D-F||B and F|
The strong tendency to resolve the dominant seventh to the tonic (GBDF to CEG) creates a resolution with which many composers throughout history have used to to end a piece of music.
The makeup of the major scale is not symmetrical, hence certain harmonic combinations will result in different chord qualities. If we use C major scale for example:
A four note chord from the 1st degree will result in a major seventh chord.
C MA7 Chord Construction From the 1st Degree
A four note chord from the 4th degree will result in a major seventh chord.
F MA7 Chord Construction From the 4th Degree
By Contrast, a four note chord from the 5th degree results in a dominant seventh chord. The interval between the last two notes of the chord is a minor third.
G7 Chord Construction From the 5th Degree
Dominant seventh chords can be thought of in a number of different ways:
1. The dominant seventh chord is achieved by lowering the 7th degree of a major seventh chord.
C7 Chord Construction By Lowering the 7th Degree of C MA7
2. It can be constructed by adding the minor seventh to a major triad.
C7 Chord Construction By Adding a Minor 7th to C Major Triad
Some composers choose to pass their melodies through a number of keys. This process is called modulation.
Dominant seventh chords are used by composers almost exclusively to carry out a change of key; modulation.
Example of modulation from C major to F major:
|C MA7||F MA7||C MA7||C7||F MA7|