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.
A Perfect Authentic Cadence (PAC) is the gold standard of musical closure. To earn the "perfect" label, three boxes have to be checked: the dominant chord (V or V⁷) is in root position, 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. 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.
The PAC lives in Topic 5.5 (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, 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 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.
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Visual cheatsheet
view galleryAuthentic Cadence (Unit 5)
Every PAC is an authentic cadence, 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 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)
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)
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 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.
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.
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.
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.
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.
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.
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.
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.
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