Phrase and Cadence

A phrase is the smallest complete musical thought — typically about four bars long, ending with a cadence (a harmonic gesture that punctuates the phrase like a comma, semicolon, or period).

Think of a phrase like a sentence. It has direction, an arrival point, and a sense of closure (or pointed non-closure) at its end. Without phrases, music is just notes.

The Structural Ladder

Unit	Size	What it does
Motif	2–7 notes	The DNA — the shortest recognizable idea
Phrase	~4 bars	Ends with a cadence, usually a weak one
Period	~8 bars (2 phrases)	Antecedent + Consequent — see Period vs Sentence
Sentence	~8 bars (different logic)	Presentation + Continuation + Cadence
Double period	~16 bars (4 phrases)	Bigger arc — only the final cadence fully resolves

The Five Cadences

Cadence	Chords	Strength	Feel
Perfect Authentic (PAC)	V → I, both in root position, soprano on tonic	Strongest	Full stop. The end.
Imperfect Authentic (IAC)	V → I, but with inversion or non-tonic soprano	Strong	Stop, but with momentum forward
Half Cadence	Anything → V	Weak	Comma. Phrase pauses, expects a continuation
Plagal	IV → I	Strong	"Amen" cadence — gentler than PAC
Deceptive	V → vi (or some non-tonic)	Surprise	Promised resolution, denied — extends the phrase

How Cadences Mark Phrases

A strong cadence (PAC, IAC, plagal) closes a phrase. A weak cadence (half, deceptive) leaves the phrase open, demanding a follow-up phrase to provide the closure.

The interplay between weak and strong cadences is how composers organize phrases into larger structures. A typical period:

Phrase 1 (antecedent) — ends with a half cadence (weak; "I'm pausing, more to come")
Phrase 2 (consequent) — ends with a PAC (strong; "now we're done")

That's the basic period. Phrase 1 asks the question; phrase 2 answers it.

Why This Matters for Your Writing

If you're composing without thinking about cadences, your phrases probably don't end clearly and your form probably doesn't have shape. You can fix 80% of "this music feels meandering" by being intentional about where your cadences fall and how strong they are.

A working compositional rule: every phrase should end with a recognizable cadence. The cadence doesn't have to be classical — pop music uses plagal cadences, modal cadences, suspended cadences, drum-fill cadences. The principle is: the phrase must arrive somewhere.