G-flat major plagal cadence

The Solution below shows the G-flat major plagal cadence on the piano and treble clef.

The Lesson steps then describe the cadence structure in this key, the chords used, followed by an example of its use.

For a quick summary of this topic, have a look at Cadence.

Solution

1. G-flat major plagal cadence

The plagal cadence moves from the subdominant (IV), to the tonic (I) scale degree.

So in this major key, we are going from the Gb major triad chord #IV - Cb major chord, to Gb major triad chord #I - Gb major chord.

This is more commonly known as the Amen cadence, used at the end of many hymns.

To demonstrate this, on the treble clef above, chords Gb major triad chord #I and Gb major triad chord #V are used to set up the phrase as being in this key, then the cadence chords IV and I finish off the phrase, giving only a partial sense of completion, in comparison to the Gb major perfect authentic cadence.

Lesson steps

1. Cadence Types

Cadence definition

In music theory, a cadence is two chords which create a sense of closure, or rest to a phrase, section, or entire piece of music.

The most commonly used are: perfect authentic, imperfect authentic, plagal, deceptive and half cadence.

Some of the above are US-english terms. In the UK, authentic cadences are called perfect cadences, half cadences are called imperfect cadences, and deceptive cadences are called interrupted cadences.

Cadences - strong versus weak

Each of the above cadence types use different chords (or inversions) to create these rest / closure effects.

Strong cadences give a real sense of finality, and so are most often used right at the end of a piece.

In contrast, weak cadences are less conclusive, which can be used to create a sense of rest, or even surprise the listener with a false ending, when a strong cadence was expected in its place.

2. G-flat major scale notes and chords

Before describing the details of the plagal cadence in the key of G-flat major, first it would be to useful to identify the scale notes, degrees and chords that could be used in this key.

G-flat major scale notes

Below is a piano diagram showing the Gb major scale notes.

G-flat major scale chords

For details on all the chords in this scale, have a look at Gb major triad chords, and Gb major 7th chords, but a summary table of all chord names and their scale degrees is shown below.

For each note in the scale (2nd column), there is a triad chord whose root / first note is that scale note (4th column), and the same applies to 7th chords (5th column).

To understand what the roman numerals mean, please look at Gb major triad chords or Gb major 7th chords.

According to the cadence type, some of these chords, scale degrees and roman numerals will be used in later steps to define this cadence.

3. G-flat major plagal cadence

Structure

The plagal cadence moves from the subdominant (IV), to the tonic (I) scale degree.

So looking up the chords relating to these scale degrees from the table above, we are going from the Gb major triad chord #IV - Cb major chord, to Gb major triad chord #I - Gb major chord.

This is known as the Amen cadence because of its use in at the end of hymns.

It is a weaker closure than the Gb major perfect authentic cadence, whose dominant to tonic motion is the most important relationship in a diatonic scale, and gives the strongest sense of closure of all cadences.

Example

The two chords above are shown as the last two chords on the treble clef below.

The first two chords on the staff below are not strictly part of the cadence, but they are useful to set the expectation that this phrase is definitely in the key of G-flat major.

To do this, we are using chords Gb major triad chord #I and Gb major triad chord #V, and after hearing these chords, the ear could expect to hear chord I again.

The audio files below also contain all 4 chords shown on the treble clef above.

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