In this guide...
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Let's look at progressions of chords at the end of each musical phrase: cadences. This is the most important area in which chords work together to define a key and give shape to the music.
Consider this limerick:
There was an old man from Peru
Who dreamt he was eating his shoe.
He awoke in a fright
In the middle of the night
And found it was perfectly true.
You will probably be very familiar with the pattern of rhymes in a limerick - A, A, B, B, A. Another characteristic of this limerick is the way in which it forms two distinct sentences, each ending with a full stop.
Thinking of the limerick musically, we could say that it consists of two long phrases (equivalent to the two sentences). The full stop at the end of each sentence acts as a kind of "closure" to that sentence - a definite end.
In music, we call a phrase-ending like this a cadence point, and the sequence of two chords (the final chord and the penultimate chord) that are used at this moment are called a cadence.
Looking at the limerick even more closely in terms of phrases, we can say that each of the five lines forms a mini-phrase in itself - so, the first big phrase consists of two mini-phrases (There was an old man from Peru / Who dreamt he was eating his shoe), and the second big phrase consists of three mini-phrases (He awoke in a fright / In the middle of the night / And found it was perfectly true).
Each of these mini-phrases also represents a cadence point, but the major cadences in this limerick are the end of each sentence.
In a musical context
Let's look at cadences in a musical context - the beginning of the Christmas carol "It came upon the midnight clear":
It came upon the midnight clear,
That glorious song of old,
From angels bending near the earth
To touch their harps of gold.
Now look at the music for these words, which is in F major, and in particular look at the chords which form the cadences indicated at the end of each line of text:
Types of cadence
There are two types of cadence which you are likely encounter at this level:
- Cadences that end on the tonic (
- Cadences that end on the dominant (
Of the first type - cadences that end on the tonic - the two most common are, the perfect cadence and the plagal cadence. Because these cadences end on the tonic, they have a very firm "finish" and tend to function as "full stops", as endings.
There is just one cadence of the second type (ending on the dominant), and that is the imperfect cadence.
You may already have come across these three cadences in aural skills tests for practical exams and learned to recognise their sound.
The perfect cadence
The perfect cadence is the strongest type of closure that a cadence can provide - a full stop and end of paragraph, for example - and consists of a dominant chord followed by a tonic chord.
The tonic chord will be in root position, and the dominant chord will usually be in root position, because the
V-I pattern in the bass is a very prominent part of this cadence, and an important way to close a phrase.
You can see a perfect cadence in "It came upon the midnight clear" above, corresponding to the end of the second line of the text, in bar 8.
Some reasons that a perfect cadence provides such a firm ending or "sense of closure" are:
- The movement of the dominant to the tonic in the bass;
- The movement of the leading note to the tonic elsewhere in the harmony;
- The combination of these two factors in fully defining the tonic key.
We sometimes simply call the perfect cadence a
V-I cadence, and both are equally valid terms, but you will need to be able to recognise both.
The example above is written in four-part harmony, and this is a common way to write down cadences for illustration and clarity. It is not the only way, however, and just as harmony doesn't necessarily happen all at once (a chord can be "broken" for example), so a cadence doesn't necessarily consist of two block chords.
Here is a short example showing how cadences can be found even in purely melodic music. Try playing both of these examples and listen out for the cadence: it should be equally recognisable in the melodic example as in the four-part example!
The plagal cadence, like the perfect cadence, ends on the tonic, but is preceded by a subdominant chord:
If you have performed any choral church music, you are likely to have come across the distinctive sound of a plagal cadence harmonising an "Amen" at the end of a hymn or sung prayer, and indeed this cadence is sometimes called an "Amen cadence".
You can see a plagal cadence in "It came upon the midnight clear" above, corresponding to the end of the first line of the text, in bar 4.
Here are two more phrases ending in a plagal cadence:
If you play these examples on the piano, you might notice that the plagal cadence is not a very strong cadence - it does not really have a strong sense of closure, unlike the perfect cadence.
The plagal cadence lacks the features listed above for the perfect cadence, and therefore cannot adequately define the tonic key: most audibly, the lack of movement from leading note to tonic.
The imperfect cadence could be considered the "opposite" of a perfect cadence. It always ends on a dominant chord, and can be preceded by a tonic chord:
I-V (unlike the perfect cadence, which is the opposite:
The imperfect cadence can also consist of
V preceded by any other chord, and the most common variations are
You can see two
I-V imperfect cadences in "It came upon the midnight clear" (above), corresponding to the end of the first and third lines of text, in the middle of bars 2 and 6. This is very much how the imperfect cadence is used - to signal a pause or "half-way point", but also signalling an expectation that there is more to come - much like a comma in the middle of a long sentence. Indeed, the imperfect cadence is also commonly known as the half cadence.
Two further imperfect cadences are shown here:
Functions of cadences: in summary
We have seen in "It came upon the midnight clear" examples of all three types of cadences (perfect, plagal, and imperfect). Looking at where they come in the four lines gives a very good idea of their relative functions in music:
It came upon the midnight clear, [imperfect]
That glorious song of old, [plagal]
From angels bending near the earth [imperfect]
To touch their harps of gold. [perfect]
As explained above, the perfect is the "strongest" closing cadence, with the plagal offering a weaker sense of closure, and the imperfect offering no sense of closure at all - it actually does the opposite, providing a sense of expectation.
The composer of this hymn (Arthur Sullivan - of Gilbert & Sullivan fame!) has used imperfect cadences to set up an expectation half-way through each pair of lines, and a perfect cadence at the end of the four lines.
However, rather than use a perfect cadence at the end of the second line, he has cleverly used a plagal cadence, which gives only a partial sense of closure - as if he wanted the music to say "but wait, there's more!"
Dominant seventh chords in cadences
It is extremely common to find a dominant seventh in a perfect cadence, because it so strongly resolves to
Any of the examples in this guide could use
V7 instead of
V in a perfect cadence.
However - you would never use
V7 in an imperfect cadence (e.g.,
I-V7). This would leave too strong a sense of incompletion!