---
title: "Perfect Authentic Cadence — AP Music Theory Definition"
description: "A Perfect Authentic Cadence (PAC) is a root-position V(7)-I with scale degree 1 in the soprano. Learn how PACs close phrases and show up on AP Music Theory FRQs."
canonical: "https://fiveable.me/ap-music-theory/key-terms/perfect-authentic-cadence"
type: "key-term"
subject: "AP Music Theory"
unit: "Unit 5"
---

# Perfect Authentic Cadence — AP Music Theory Definition

## Definition

A Perfect Authentic Cadence (PAC) is a phrase-ending progression where a root-position V or V⁷ resolves to a root-position I (or i), with scale degree 1 in the soprano voice. It's the strongest cadence in tonal music, the one that makes a phrase sound completely finished.

## What It Is

A Perfect Authentic Cadence (PAC) is the gold standard of musical closure. To earn the "[perfect](/ap-music-theory/unit-2/interval-size-quality/study-guide/HxrxB0vETN0eDp83zij1 "fv-autolink")" label, three boxes have to be checked: the dominant chord (V or V⁷) is in [root position](/ap-music-theory/key-terms/root-position "fv-autolink"), the tonic chord (I or i) is in root position, and the soprano lands on scale degree 1. Change any one of those (invert a chord, end the melody on 3 or 5) and you've downgraded to an imperfect authentic cadence.

Think of cadences as punctuation. A half cadence is a comma, a deceptive cadence is a plot twist, and a PAC is a period at the end of the sentence. That full-stop quality comes from voice leading you already know from [Unit 4](/ap-music-theory/unit-4 "fv-autolink"). The leading tone pulls up to tonic, and if there's a chordal seventh, it resolves down by step. When all those tendency tones resolve at once over a root-motion bass (5 down to 1), there's nothing left unresolved, which is exactly why the PAC defines tonal centers so convincingly.

## Why It Matters

The PAC lives in [Topic 5.5](/ap-music-theory/unit-5/cadences-predominant-function/study-guide/INNHEx3QCfTJPy2yXPqC "fv-autolink") (Cadences and Predominant Function) under learning objective 5.5.A, which asks you to identify cadence types in both performed and notated music. That means you need to recognize a PAC by ear in contextual listening and by eye in a score, and tell it apart from imperfect authentic, half, plagal, and deceptive cadences. The [deceptive cadence](/ap-music-theory/key-terms/deceptive-cadence "fv-autolink"), in fact, is defined by what it avoids: the V-I resolution that authentic cadences deliver (PIT-2.I.3).

It also connects back to [Topic 4.5](/ap-music-theory/unit-4/voice-leading-with-seventh-chords-inversions/study-guide/dIhXWfvKiWKh2bRfTjyE "fv-autolink") and learning objective 4.5.A, because writing a correct PAC is a voice-leading task. The 18th-century procedures tested on the exam (resolve the leading tone, resolve the chordal seventh down by step, avoid parallels) are exactly what makes a V⁷-I cadence work on paper. Phrase structure questions lean on PACs too. In periods and double periods, the whole form hinges on a weaker cadence (often a half cadence or IAC) being answered by a conclusive PAC at the end.

## Connections

### [Authentic Cadence (Unit 5)](/ap-music-theory/key-terms/authentic-cadence)

Every PAC is an [authentic cadence](/ap-music-theory/key-terms/authentic-cadence "fv-autolink"), but not every authentic cadence is perfect. The V-I motion makes it authentic; root position chords plus scale degree 1 in the soprano are what upgrade it to perfect.

### Voice Leading (Unit 4)

A PAC is 18th-century voice leading at its most concentrated. [Leading tone](/ap-music-theory/key-terms/leading-tone "fv-autolink") up to tonic, chordal seventh down by step, bass leaping 5 to 1. The Composition FRQ grades your cadence on exactly these moves.

### [Leading Tone (Units 4-5)](/ap-music-theory/key-terms/leading-tone)

The leading tone's pull toward tonic is the engine of the PAC. In minor keys you have to raise scale degree 7 in the V chord, or your "authentic" cadence loses its drive and your Roman numerals lose points.

### [Harmonic Rhythm (Unit 5)](/ap-music-theory/key-terms/harmonic-rhythm)

Cadences usually land on metrically strong beats, and harmonic rhythm often slows or settles at a PAC. Hearing where the harmony comes to rest helps you find cadences in contextual listening questions.

## On the AP Exam

On the multiple-choice section, you'll identify cadences in notated excerpts and by ear, so you need the PAC checklist memorized: root-position V(7), root-position I, soprano on 1. Expect distractors that are technically authentic but imperfect (soprano ends on 3 or 5, or a chord is inverted). Phrase-structure questions also use PACs as evidence, like identifying why the end of a double period sounds more final than the cadence halfway through. The answer is almost always that the consequent group closes with a PAC while the antecedent group ends with something weaker.

On the free-response section, the bass-line Composition question (Question 7 in 2023, 2024, 2025, and 2026) asks you to complete a bass line with Roman and Arabic numerals following 18th-century voice-leading procedures. These melodies are built to end with an authentic cadence, so writing a clean root-position V(7)-I with correct tendency-tone resolution at the end is where reliable points live. Embellishments matter too; an anticipation tone in the melody at a PAC briefly sounds the tonic note against the V chord, adding tension right before the resolution.

## Perfect Authentic Cadence vs Imperfect Authentic Cadence (IAC)

Both are V-I cadences, so both are "authentic." The difference is strength. A PAC has both chords in root position and scale degree 1 in the soprano. An IAC breaks at least one of those rules, maybe the soprano ends on 3 or 5, or the V is inverted. On the exam, the soprano note is the detail most people forget to check. If the melody ends on anything other than the tonic pitch, it's not perfect.

## Key Takeaways

- A Perfect Authentic Cadence requires a root-position V or V⁷ moving to a root-position I (or i), with scale degree 1 in the soprano voice.
- The PAC is the strongest cadence in tonal music and signals complete closure, like a period at the end of a sentence.
- If the soprano ends on scale degree 3 or 5, or either chord is inverted, the cadence is an imperfect authentic cadence, not a PAC.
- In periods and double periods, the final phrase typically ends with a PAC, answering a weaker cadence (like a half cadence) earlier in the form.
- Writing a PAC correctly means resolving the leading tone up to tonic and the chordal seventh down by step, which is exactly what the bass-line Composition FRQ rewards.
- In minor keys, you must raise the leading tone in the V chord for the cadence to function as authentic.

## FAQs

### What is a Perfect Authentic Cadence in AP Music Theory?

It's a phrase-ending progression where a root-position V or V⁷ resolves to a root-position I (or i in minor), with scale degree 1 as the highest note. It creates the strongest sense of finality of any cadence and is the main way music establishes its tonal center.

### Is every V-I cadence a Perfect Authentic Cadence?

No. V-I is authentic, but it's only perfect if both chords are in root position and the soprano ends on scale degree 1. A V-I where the melody ends on 3 or 5 is an imperfect authentic cadence, which sounds conclusive but less final.

### What's the difference between a PAC and a half cadence?

A PAC ends on the tonic (V-I) and sounds finished, while a half cadence ends on V itself and sounds open, like a question waiting for an answer. In a typical period, the antecedent phrase ends with a half cadence and the consequent answers it with a PAC.

### Does a Perfect Authentic Cadence work the same in minor keys?

Yes, but you have to raise scale degree 7 so the V chord is major and contains a true leading tone. The progression is V (or V⁷) to i, with scale degree 1 in the soprano, just like in major.

### Do I need to write a PAC on the AP Music Theory FRQs?

Effectively yes. The bass-line Composition question (Question 7 on the 2023-2026 exams) asks you to harmonize a melody using 18th-century voice-leading procedures, and those melodies end with an authentic cadence. A clean root-position V(7)-I with proper leading-tone and seventh resolution is how you earn the closing points.

## Related Study Guides

- [5.5 Cadences and Predominant Function](/ap-music-theory/unit-5/cadences-predominant-function/study-guide/INNHEx3QCfTJPy2yXPqC)
- [Unit 8 Overview: Modes and Form](/ap-music-theory/unit-8/review/study-guide/azh0orlEVNX2vpDvh1Ld)
- [4.5 Voice Leading with Seventh Chords in Inversions](/ap-music-theory/unit-4/voice-leading-with-seventh-chords-inversions/study-guide/dIhXWfvKiWKh2bRfTjyE)
- [8.2 Phrase Relationships ](/ap-music-theory/unit-8/phrase-relationships/study-guide/diwcsRGh8jxcbua8l2BA)
- [6.3 Embellishing Tones: Identifying Anticipations, Escape Tones, Appoggiaturas, and Pedal Points](/ap-music-theory/unit-6/identifying-anticipations-escape-tones-appoggiaturas-pedal-points/study-guide/qIBADFw1MYL3dIF3FZzX)

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