In music theory, the key of a piece refers to the tonal center or home note. This establishes the relationship between all the tones and chords in a composition. The key is determined by the key signature, which is the scale degree represented by the tonic or home note. When a key signature has major and minor chords built on it, it is referred to as the dominant key.
What is a Key Signature?
A key signature is a series of sharps or flats at the beginning of the staff, right after the clef, that indicates the key of the music. It shows which notes should be played higher or lower throughout the piece. The key signature determines the scale used, what chords will sound most consonant, and which chord progressions will work well in the song. Every major and minor key has a unique key signature.
Purpose of Key Signatures
Key signatures serve several important purposes:
- They eliminate the need to indicate sharps and flats repeatedly throughout the music.
- They visually convey the home key and tonic chord.
- They show which notes are raised or lowered throughout the piece.
- They determine which chords and chord progressions will sound best.
By having the key signature at the start, both the performers and the reader know what to expect in terms of accidentals and harmony.
What is a Tonic?
The tonic is the first scale degree of a key and the note of resolution. It is what establishes the sense of home or rest within the key. The tonic triad, built off the tonic note, is the most consonant and stable chord.
In the key of C major, the tonic note is C. In the key of A minor, the tonic note is A. The tonic determines the central note that the melody and chords revolve around.
Examples of Tonics
| Key | Tonic |
|---|---|
| C major | C |
| F# minor | F# |
| Eb major | Eb |
| Bb minor | Bb |
What is the Dominant?
The dominant is the fifth scale degree of a major or minor key. It has a strong pull towards the tonic chord, creating tension that wants to resolve. In a major key like C major, the dominant note is G. In a minor key like A minor, the dominant note is E.
Characteristics of the Dominant
The dominant has several important characteristics:
- It is a perfect fifth above the tonic.
- It creates a dominant seventh chord that wants to resolve to the tonic.
- It establishes tension that pulls towards the tonic for resolution.
- It is considered an unstable chord, whereas the tonic is stable.
These tendencies give the dominant an active, urgent feel that builds anticipation for the tonic chord. This creates forward momentum in the harmony.
The Dominant Chord
The dominant chord is a major triad built on top of the dominant scale degree. For example, in C major, the dominant chord is G major. In A minor, the dominant chord is E major.
The dominant chord also takes a minor seventh, making it a dominant seventh chord. So in C major, the dominant seventh chord would be G7 (G-B-D-F).
Dominant 7th Chord Formula
The formula for a dominant seventh chord is:
- Root – Major 3rd – Perfect 5th – Minor 7th
This chord contains the dissonant tritone interval between the third and the seventh, creating an unstable sound that wants to resolve to the tonic chord. Playing the dominant seventh leads the ear to expect the tonic.
Dominant Function
Due to its tendency toward the tonic, the dominant chord has a strong functional role in harmony. It has a dominant function – it creates tension and expectations for resolution.
Even chords that are not built on the fifth scale degree can have a dominant function if they create that pull toward the tonic. For example, in C major, an A dominant seventh chord can be used for its dominant function to lead to a D minor chord.
Characteristics of Dominant Function
Chords with dominant function have these traits:
- Major quality
- Minor 7th added
- Active, urgent tone
- Pull toward tonic due to the tritone
Recognizing this function allows composers to use dominants flexibly to control the harmonic momentum.
The Dominant Key
Now that we have covered the dominant chord and its role, we can look at the dominant key. When a key signature has a dominant chord built on it, it is called the dominant key. The dominant key is always a perfect fifth above the home or tonic key.
Example of a Dominant Key
Let’s take the key of C major:
- The tonic note is C.
- The dominant note is G.
If we build a key signature based on G as the tonic, we get the key of G major. The key of G major is the dominant key relative to C major. The G major chord is the dominant in the key of C.
This relationship works the same way in minor keys. For instance:
- In A minor, the tonic is A and the dominant is E.
- E minor is the dominant key relative to A minor.
This dominant key relationship is fundamental to harmony and key progressions in Western music.
How Does the Dominant Key Create Tension and Resolution?
The dominant key creates a feeling of rising tension because it contains the dominant chord from the home key. This dominant chord (like G7 in C major) pulls strongly toward the tonic chord (C major).
When you modulate to the dominant key, this creates momentum and expectations toward resolution back to the tonic key. composers can use this tension creatively within their chord progressions.
For example, moving from C major to G major temporarily feels unsettled because it contains the G7 dominant chord. This makes the listener anticipate a resolution back to the more stable C major tonic.
Importance of the Dominant Key
Understanding the dominant key and dominant function gives composers a tool to control the feeling of tension and resolution in a composition. Here are some key points about the dominant in music:
- The dominant chord contains a tritone and wants to resolve to the tonic.
- Modulating to the dominant key increases tension and expectation.
- Dominant function can be used creatively with chords outside the key signature.
- The relationship between tonic and dominant keys is fundamental in Western harmony.
Learning to use the dominant key, chords, and function expands a composer’s ability to control the listener’s musical experience.
Summary
In summary, here are the key points about dominant keys:
- The key signature establishes the tonic or home note of a piece of music.
- The tonic chord sounds the most stable and consonant.
- The dominant is the fifth scale degree and has a strong pull toward the tonic chord.
- Dominant seventh chords contain a tritone and want to resolve to the tonic.
- Chords with dominant function lead to the tonic due to their unstable sound.
- The dominant key is a fifth above the tonic key and contains the dominant chord from the home key.
- Modulating to the dominant key increases tension that wants to resolve back to the tonic key.
Understanding these concepts allows composers to create more interesting harmony and manipulate musical tension and resolution.