Chords may have different functions depending on the interval they contain and how they are used. In this article we talk about the dominant chord function, and how it can be used in guitar chords.
Based on that, it is possible to classify chords in one of a few functions that they can assume in a song.
These are some of the most common chord functions used in traditional music:
- Tonic: this function is particular to the tonic of a key, and it can be a major or a minor chord, depending on the type of key. There may be some variations too, such as added notes such as the major seventh, ninth, eleventh, and thirteenth.
- Subdominant: The subdominant is the chord below the dominant, that is, the forth degree of the scale. So, if you have an E major key, the subdominant is the A chord. There are other chords that substitute for the A chord, such as the F#m, which also has the same subdominant function.
- Dominant function: some chords have the function of dominant. The most important are the chords on the 5th degree, or dominant. In the key of E, the dominant is B7.
The Dominant Chords
The basic dominant chord is the firth chord with 7th. For example, we have E7 as the dominant chord for A.
This basic sequence of chords is denoted as V-I, or 5-1.
The dominant chord is very common in traditional harmony because it precedes the resolution to the tonic. Thus, the 5-1 sequence of chords leads to the tonic chord.
The typical composition of the dominant chords is notes 1, 3, 5, and 7 of the major scale.
For example, in C major we have the dominant as G7. The G7 chord contains the following notes: G,B,D,F.
In another example, in A major we have the dominant as E7. The E7 contains the following notes: E,G#,B,D:
It is important to notice in this chord that there are two notes, B and F, that are just one semitone from two other notes in the scale: C and E. This creates a natural tendency for the dominant chord to lead into the tonic chord.
Moreover, the C and E are the tonic and third of the C major scale, which determines that the movement leads to the C major scale. This is what makes the dominant chord so important in leading to the tonic.
Substitutions
Other chords can also substitute for the dominant, but with the same function.
See, for example, the D# dim chord. This chord contains the notes D#,F#,A, and C. These are very similar to the notes in B7: B,D#,F#,A, with the only difference in the B note.
This means that D# approximates the B7 chord. And in fact, we can in many cases use the D# dim chord as a substitution for B7.
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