Cadences are found at the end of musical phrases. They are used in much the same way as a full stop or a comma is used in writing, that is, they reinforce the feeling of rest at the completion of a musical idea. Harmony, melody and rhythm all work together to complete a phrase. Like the full stop and comma from the punctuation analogy, which produce different degrees of pause or complete rest in a sentence, there can be varying degrees of finality which a cadence may produce, and there are four main types of cadences to achieve these degrees.
Of the four cadence types, it is the perfect cadence which is the most final sounding. The perfect cadence is formed by a move from the dominant to the tonic of a key, V – I.
This finality is caused by the leap from the fifth of the key to the root, and also the resolution, upwards, of the leading note to the tonic.
It is this combination of resolutions which creates a strong feeling of rest and completion. The perfect cadence can be used at any cadential point, but it is almost always used as the final cadence in a piece of music. In this context the tonic note is typically found in both the bass and melody of the tonic chord, as in the examples above, which adds to the feeling of finality.
When a seventh is added to the dominant chord, to create a dominant seventh, the ‘pull’ towards the tonic chord is made even stronger. This is due to the tritone formed between the seventh and leading note of the dominant seventh chord, which needs to resolve. In the example below, the tritone is between the E and B flat notes
When a perfect cadence completes an entire work or movement, the tonic chord will always be in root position. There is, however, the possibility for either, or both of the two chords to be inverted, especially for internal cadences.
Of course, these examples all work in minor keys also.
The plagal cadence is formed by a move from the subdominant to the tonic, IV – I.
Because it lacks the leading note, the plagal cadence is less final sounding than the perfect cadence.
The imperfect cadence differs from the other cadence types as it ends on the dominant. It is often used in situations where two phrases have a natural resting point on V at the end of the first phrase before moving to I at the end of the second phrase.
In this way, the two phrases can be viewed either as a longer phrase punctuated by the dominant, or two shorter phrases, one ending on V and the other ending on I.
Imperfect cadences typically use various chords to precede the dominant; these are often I, ii, IV or VI.
Because they move to the dominant, imperfect cadences sound unresolved, as if they need to continue on to another destination. As such, they are used as a temporary resting place before the music proceeds to the next cadence.
As its name suggests, the interrupted cadence begins like a perfect cadence, it starts on the dominant, but instead of a resolution to the tonic, the interrupted cadence moves to another chord; typically the submediant, V – vi.
The cadential six-four is often thought of as consisting of three separate vertical entities: a second inversion tonic chord, the dominant, and the tonic – which is typically either in root position or first inversion.
This description may identify the vertical elements but it doesn’t explain the function of the notes of the ‘second inversion tonic,’ which are essentially intensifying the perfect cadence. If we change the chord labels slightly,
we can begin to see the true underlying cadential movement.
An explanation of the origins of the cadential six-four may clarify this concept.
Early voice-leading at cadences invariably included a 4-3 suspension which delayed the leading note while creating dissonance.
The fifth of the dominant could also be delayed by the interval of a 6th
Over time composers began to use this ‘six-four’ on its own; without the accompanying suspension. Because it is still essentially an embellishment of the dominant, the preferred label is as shown
This label may cause confusion if we forget that the figures indicate the voice-leading above the dominant and not that the dominant is in second inversion. Occasionally, the cadential six-four moves to a dominant seventh.
Here, the doubled root of the dominant (E) moves to the seventh (D) and on to the third of the tonic (C). It will be noticed that typically the voice-leading in the cadential six-four is by step.
The cadential six-four must appear in a metrically strong position. In other words, the six-four will move from a strong beat to a weak beat.