Cadences

The full cadence

I–IV–V–I · C – F – G – C · T–S–D–T

Tonic, subdominant, dominant, tonic — the basic formula that establishes a key. Between them the three primary triads hold all seven notes of the scale.

Authentic cadence (perfect cadence)

V–I · G – C · D–T

Dominant to tonic: the ending that sounds like a full stop. It is called perfect when both chords are in root position and the melody ends on the root.

Plagal cadence

IV–I · F – C · S–T

Subdominant to tonic: the »Amen« at the end of hymns. Softer than the authentic cadence because no leading note pulls to the root.

Half cadence

I–V · C – G · T–D

Ends on the dominant: a comma, not a full stop. The phrase stays open and you expect it to continue.

Deceptive cadence (interrupted cadence)

V–vi · G – Am · D–Tp

The dominant resolves not to the tonic but to the relative minor: the ear expects C major and gets A minor. That is how a phrase is extended.

Phrygian half cadence (in A minor)

iv⁶–V · Dm/F – E · s–D

In minor: the subdominant in first inversion falls a semitone to the dominant. That step in the bass sounds Phrygian — Baroque and flamenco.

How to tell them apart

Listen to the last chord. Tonic at the end: authentic cadence (from the dominant) or plagal cadence (from the subdominant). Dominant at the end: half cadence. A dominant that does not go to the tonic: deceptive cadence.