Types of cadences: how phrases end

Punctuation, in effect. A phrase of music arrives somewhere, and the last two chords say what kind of arrival it was — a full stop, a comma, or a sentence that breaks off.

Naming differs across traditions. British teaching says perfect, imperfect, plagal and interrupted; American teaching says authentic, half, plagal and deceptive. They describe the same four things, and both sets of names appear below.

Perfect (authentic): V–I. The dominant resolves to the tonic. In C major: G to C. The strongest ending there is, and the reason most pieces close this way. When both chords are in root position and the melody lands on the tonic, it is a perfect authentic cadence — the most conclusive version.

Imperfect (half): anything–V. The phrase ends on the dominant, so it stops without settling. In C major: ending on G. It is the musical equivalent of a comma, and it is what makes a first phrase demand a second.

Plagal: IV–I. Subdominant to tonic. In C major: F to C. Softer than perfect, and known as the amen cadence because hymns end that way. It confirms an ending rather than creating it — often used after a perfect cadence has already closed the phrase.

Interrupted (deceptive): V–vi. The dominant sets up the tonic and goes to the relative minor instead. In C major: G to Am. The ear expects home and gets somewhere adjacent, which extends the phrase and is why so many songs use it before a final chorus.

Phrygian half cadence: iv6–V in minor. A specific and recognisable form of half cadence, common in Baroque slow movements, where the bass steps down a half step to the dominant.

Imperfect authentic cadence. A V–I where something weakens the arrival — one chord inverted, or the melody landing on the third or fifth rather than the tonic. Same chords as a perfect cadence, less finality, and useful mid-piece where a full stop would be too much.

Play I–IV–V–I in any key and stop on the V. The urge to continue is the half cadence; satisfying it is the perfect cadence. That single experiment teaches more than the definitions do.

Then repeat it and go to vi instead of I. The feeling of being let down gently is the deceptive cadence, and once you have heard it deliberately you will recognise it in songs you already know.

The plagal is easiest of all to identify: it is the sound at the end of a hymn, and of countless rock songs that add a F–C tag after the last chorus.

They shape sections. A verse that ends on the dominant pulls into the chorus; a verse that ends on the tonic stands complete and needs something else to justify continuing.

They also mark form. Analysts identify phrase boundaries by cadences, and the pattern of half cadences answered by perfect ones is what gives classical themes their question-and-answer shape.

In songwriting the useful move is the deceptive cadence before a final chorus: it delays the arrival by one chord and makes the eventual resolution land harder.

A cadence ends a phrase; musical form is the same question asked about whole sections. Cadences are built from the chords of the key, and moving to a different key mid-piece is modulation.