Cadences & Phrase Structure

You’ll be able to

Identify the cadence types by their chords and voicing
Distinguish perfect from imperfect authentic cadences
Describe phrases, periods, and antecedent–consequent structure

Cadences: musical punctuation

A cadence is the harmonic goal that ends a phrase, functioning like punctuation. The main types: an authentic cadence moves V (or V7) → I and sounds conclusive; a half cadence (HC) ends on V, sounding like a comma or question; a deceptive cadence (DC) sets up V but resolves V → vi, dodging the expected tonic; and a plagal cadence (PC) moves IV → I, the "Amen" ending often used as a soft afterword to an authentic cadence.

Perfect vs. imperfect authentic cadences

Not every V–I is equally final. A perfect authentic cadence (PAC) meets three conditions: both chords are in root position, and the soprano ends on the tonic (do). It is the strongest, most closed ending. An imperfect authentic cadence (IAC) is still V–I but weaker because it breaks one of those conditions — a chord is inverted, or the soprano lands on the third or fifth (mi or sol) instead of the tonic. The soprano note and the bass positions are what you check to tell them apart.

Phrases and periods

A phrase is a complete musical thought ending in a cadence, often about four measures. Two phrases can combine into a period: an antecedent phrase ends with a weak cadence (usually a half cadence — the "question"), and a consequent phrase answers it, ending with a stronger cadence (usually a PAC — the "answer"). If both phrases begin with the same material it is a parallel period; if they begin differently, a contrasting period.

Cadence chord templates

PAC/IAC: V(7) → I · HC: … → V · DC: V → vi · PC: IV → I

PAC additionally requires both chords in root position and the soprano ending on do. Break either condition and V–I becomes an IAC.

Worked example

A phrase in C major ends with a G7 chord moving to an A minor chord, where you expected the tonic. Name and explain the cadence.

1.Identify the chords: G7 is the dominant (V7) in C major; A minor is the vi chord.
2.V normally resolves to I (C major) for an authentic cadence.
3.Here V resolves instead to vi (A minor), thwarting the expected arrival on tonic.
4.A dominant that "deceives" by moving to vi is the deceptive cadence.

Answer: It is a deceptive cadence (V–vi): G7 (V7) resolves to A minor (vi) rather than to C major (I), delaying true closure and extending the music.

Checkpoint

A phrase in C major ends with a G major chord moving to a C major chord, both in root position, with the soprano landing on C. What cadence is this?

Tip

To tell PAC from IAC, check two things only: are both V and I in root position, and does the soprano end on do? If yes to both, it is a PAC. Any inversion, or a soprano ending on mi or sol, downgrades it to an IAC.

Checkpoint

A phrase in G major pauses on a D major chord (V), sounding unfinished, like a question awaiting an answer. What cadence is this?

On the exam

In a parallel period, listen for the antecedent to end on a half cadence (the question) and the consequent to answer with a PAC. Identifying "HC then PAC" over two similar phrases is textbook evidence of a period — a frequent free-response and aural task.

Answer the 2 checkpoints as you read.