Preamble 1: How Chords Work.
At this point you may like to refer back to the worksheets titled “Degrees of the Scale” and “Building Triads”. You will remember that each degree of the scale can be given a number and a name. Let’s not worry about the names here but the numbers are important because we use them to name the chords built upon them. So,
As you can see I have numbered the chords (triads) using Roman numerals. These numbers match the number of the degree of the scale for the root of each of the triads. Upper case represents major triads and lower case represents minor triads.
Play the triads on a piano or keyboard. Notice how chords I, IV and V are the only ones that create major triads on degrees of the major scale. These are known as PRIMARY CHORDS - just as yellow, red and blue are primary colours. Most simple tunes can be harmonised just using these chords. A lot of early pop music used just these chords. This is because pop and rock and roll were based on the chord sequence of the Blues which also used these three chords.
Preamble 2: Punctuation in Music
To understand the function of cadences we need to understand how melody works. This may seem odd, as cadences are features of harmony, not melody. But melody and harmony are closely related..
Here you can see two balanced 4 bar phrases. Each of them ends with a cadence. So if a phrase is like a sentence in music then cadences are like punctuation points. They help to bring phrases to a close which is why the word “close” is an old word for a cadence.
Cadences are a chord progression which supports the end of a phrase, section or piece of music.
Perfect Cadence: Chord of V (or V7) to chord of I.
This
is by far the most common cadence in western classical music. It was really
important for establishing the major scale over the old church modes. It
establishes or confirms tonality because major scales have two semitones and
this cadence contains both of them. They act almost like gravity pulling you to
the tonic chord. The effect is a bit like a musical version of seeing a piece
of cake, wanting the piece of cake and getting the piece of cake. It’s all very
satisfying!
Imperfect Cadence: Chord of I (or any chord) to chord of V.
Imperfect Cadences are the opposite of Perfect Cadences. This cadence ends on chord V and so doesn’t have the satisfying sense of arrival or resolution that Perfect Cadences possess. Imperfect Cadences do not sound final but leave you expecting more. In Baroque and Classical music, Imperfect cadences are often used to end a first phrase such as in the example above. They rarely finish a piece unless there is an expectation of something else to come.