Authentic and Plagal Cadences

Core Idea

Cadences are chord progressions that end phrases, creating punctuation in music. The authentic cadence (V-I) is the most powerful conclusion, with dominant tension resolving to tonic. The plagal cadence (IV-I), the 'Amen cadence,' is softer and more subtle. Both signal harmonic motion's end, but they differ in strength and character.

How It's Best Learned

Listen to examples of authentic and plagal cadences, noting how each sounds at phrase endings. Play or sing both cadence types, feeling the resolution difference. Identify cadences in scores by finding final V-I or IV-I progressions.

Common Misconceptions

All cadences sound dramatic (plagal cadences are gentle). Confusing half cadences (ending on V) with authentic cadences. Assuming cadences must have root position chords (inversions are common).

Explainer

You already understand harmonic function — that chords play roles: tonic (home, stability), dominant (tension, departure), subdominant (gentle away-from-home movement). A cadence is the moment when those functions resolve into a grammatical ending. Think of cadences as punctuation marks in musical syntax: a comma for a half-stop, a period for a full stop. The two primary cadence types — authentic and plagal — use those functions in different sequences to produce different degrees of finality.

The authentic cadence moves V→I: dominant to tonic. This is the most definitive ending in tonal music because the dominant chord contains a tritone (in a major key, the interval between the leading tone and the fourth scale degree) that cries out for resolution. When that tritone resolves — the leading tone stepping up to the tonic, the fourth stepping down — the sense of arrival is powerful and unambiguous. The perfect authentic cadence (PAC) requires both chords in root position and the soprano ending on the tonic note; this is the strongest possible conclusion. The imperfect authentic cadence (IAC) uses V→I with inversions or a non-tonic soprano, producing a softer landing — still final, but less emphatic. Almost every major musical phrase in the Common Practice period ends with some form of authentic cadence.

The plagal cadence moves IV→I: subdominant to tonic. Because the subdominant chord does not contain the tritone or the leading tone, its motion to tonic lacks the driving tension of the authentic cadence. The result is a softer, more contemplative resolution — peaceful rather than conclusive. You know this sound instantly: it is the "Amen" at the end of a hymn, added after the piece has already reached its authentic cadence as a final exhale. The plagal cadence confirms arrival rather than creating it; it says "yes, we are home" rather than "we have arrived." This quality makes it useful for codas, post-cadential extensions, and modal or religious musical contexts where finality without drama is the goal.

Understanding both cadence types trains your ear to hear phrase structure — where a musical sentence ends and how decisively it ends. Pieces are built from phrases, and phrases are defined by their cadential endpoints. When you analyze a score, finding the cadences is often the first step: locate the V→I or IV→I progressions, and you have found where the phrase boundaries are. From there, you can observe how composers manipulate cadential expectations — delaying them, surprising the listener with a deceptive cadence (V→vi instead of V→I), or emphasizing them with extended dominant preparation — all techniques that depend on the listener's internalized expectation of these two cadence archetypes.