A phrase ends with V moving to I, both chords in root position. However, the soprano voice ends on scale-degree 3 rather than scale-degree 1. This cadence is:
AA perfect authentic cadence — root-position V to root-position I is all that the definition requires.
BAn imperfect authentic cadence — the soprano fails to arrive on scale-degree 1, weakening the closure despite the correct harmonic progression.
CA half cadence — because the V chord has not resolved as expected.
DA deceptive cadence — the resolution to a tonic with 3 in the soprano evades the expected arrival.
The PAC requires three conditions: V to I (or V7 to I), both chords in root position, AND the soprano ending on scale-degree 1. The soprano condition is the crucial voice-leading detail. When the soprano ends on 3 or 5 instead of 1, the top voice hasn't settled on the tonic pitch, producing an imperfect authentic cadence — harmonically the same progression, but weaker in closure. PACs end movements; IACs end phrases while leaving the door open.
Question 2 Multiple Choice
What is the 'leading-tone resolution,' and why is it considered the most important single voice-leading rule at authentic cadences?
AThe bass leaps from the fifth scale degree to the root, creating harmonic arrival through strong motion.
BScale-degree 7 in the V chord must resolve upward by half step to scale-degree 1, because its strong directional pull is the primary force creating the sense of arrival.
CThe soprano voice must descend by step into the final tonic pitch at every authentic cadence.
DAll upper voices must converge on the tonic pitch simultaneously with the bass.
The leading tone (scale-degree 7) lies a half step below the tonic, and this narrow distance creates intense upward pull — it is literally 'leading' to the tonic. In the V chord, the leading tone is the third; in V7, it is also present. Failing to resolve the leading tone upward (except in the conventional inner-voice exception to avoid parallel octaves) makes the cadence feel unfinished or evasive. Composers exploit this violation purposefully when they want that exact effect.
Question 3 True / False
A plagal cadence (IV–I) typically sounds gentler and more settled than an authentic cadence because no leading tone is involved — there is no strongly directional half-step pull toward the tonic.
TTrue
FFalse
Answer: True
The authentic cadence creates tension through the leading tone (and often the seventh in V7) that resolves by half step, producing a sense of arrival-after-tension. The plagal cadence has no such directional pressure. IV and I share two common tones (scale-degrees 1 and 3), and the bass motion from 4 down to 1 (or up a fifth) is smooth but not tense. The result is the 'amen' quality — confirming a resting state already present rather than resolving accumulated tension.
Question 4 True / False
A perfect authentic cadence and an imperfect authentic cadence use different underlying chord progressions: the PAC uses V–I while the IAC uses IV–I.
TTrue
FFalse
Answer: False
Both the PAC and the IAC use the same chord progression: V to I (or V7 to I). The difference is entirely in the voice leading, specifically the soprano. A PAC requires the soprano to end on scale-degree 1 with both chords in root position. An IAC uses the same V–I harmonic motion but has the soprano end on 3 or 5, or has one chord in an inversion. Mistaking IV–I for an IAC confuses the plagal cadence with the imperfect authentic cadence.
Question 5 Short Answer
Explain the difference between a perfect authentic cadence and an imperfect authentic cadence, and describe what makes one produce stronger closure than the other.
Think about your answer, then reveal below.
Model answer: Both use V–I (or V7–I) with root-position chords. In a PAC, the soprano must end on scale-degree 1, creating a simultaneous convergence on the tonic pitch from the bass (root position) and the top voice. In an IAC, the soprano ends on scale-degree 3 or 5, or one chord is not in root position — the harmonic arrival is present but the melodic and registral closure is incomplete. The PAC's strength comes from this double convergence: bass and soprano arrive on the tonic simultaneously, leaving nothing unresolved.
The practical consequence is significant: PACs conventionally close sections and movements — they are the final word. IACs close phrases but imply continuation; they function as breathing points, not endpoints. Composers use IACs deliberately when they want the music to feel unfinished, as at the end of an antecedent phrase that demands a consequent.