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If harmony had punctuation, it would be the cadence. A cadence decides whether a phrase has finished or is still hanging.
The four cadences
| Name | Motion | Closure | Punctuation |
|---|---|---|---|
| authentic | V → I | strongest | full stop |
| plagal | IV → I | soft, with afterglow | also a full stop, lighter in tone |
| half | any chord → V | hangs | comma or semicolon |
| deceptive | V → vi | diverted | exclamation mark |
The difference reduces to one question: which chord does it land on? Landing on the tonic closes (authentic or plagal); landing on the dominant suspends (half); landing elsewhere surprises (deceptive).
Why the authentic cadence is strongest
Because it resolves the tritone inside the dominant seventh: the leading tone rises a semitone and the seventh falls a semitone, both lines closing into the tonic at once (see harmonic function). None of the other three has that two-way clamp.
The sound of the plagal cadence
IV → I lacks the leading tone's thrust, so it lands more gently — with a sense of the curtain coming down rather than a decisive cut. It is common in church music, hymn endings and rock — reach for it when you want solemn rather than decisive.
What the deceptive cadence is for
V → vi postpones. The music is about to land and instead turns to the relative minor. Composers use it to extend a phrase: a place that should have closed does not, and the passage lengthens — a standard device for enlarging structure in melodic writing.
Cadences and form
The strength of a cadence fixes the level of the division it marks:
| Cadence strength | Unit it usually divides |
|---|---|
| weak (half) | a pause inside a phrase |
| medium (plagal, weak authentic) | the end of a phrase |
| strong (full authentic) | the end of a period, a section boundary |
Which is why the first step in analysing sonata form is finding the cadences.
Diagram: where each cadence lands
Listen: the four cadences
In order: authentic (V→I, firmest), plagal (IV→I, softer), half (I→V, hanging), deceptive (V→vi, postponed).
Common misconceptions
- "A cadence means an ending." A half cadence does not end anything; it creates expectation. A cadence is punctuation, not only a full stop.
- "The plagal cadence is a weaker authentic." It is more like a different tone of voice — solemn, relaxed, with afterglow — rather than insufficient force.
- "A deceptive cadence is a mistake." It is a deliberate postponement device, commonly used to extend phrases.
- "Cadences belong to classical music." A pop song returning to the tonic, or resting on V, can be described in exactly the same language.
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Listen in the library
All tracks from midicn-lib — inline badge is the license tier (C1 commercial / C2 non-commercial / C3 study only).
Sources
- 四种终止式（正格 / 变格 / 半 / 阻碍）的构成与收束强度差异，属和声学通则
- 终止式在曲式分析中用于划分乐句与乐段，为通行表述
Used for fact-checking only; all prose is original.