PLAGAL CADENCES

A plagal cadence is a cadence based on a plagal cadential progression i.e. a chord progression from the fourth to the first scale degree.

There is a problem with plagal cadences: they are very rare. Plagal cadential progressions appear relatively often but they typically appear after authentic cadences as a way to give more weight to the authentic cadence. In these cases, the authentic cadence is considered the ending of the complete thought. In church music, “amen cadence” occurs in this way.    

As an example, we can examine plagal cadential progressions at the ending of Chopin’s Prelude No. 1 in C major. We see the chord progression from the fourth to the first scale degree which is repeated a few times and it happens after the perfect authentic cadence.

A plagal cadence is usually annotated using the abbreviation PC.

Figure: The plagal cadential progressions at the end of Chopin's Prelude No. 1 in C major