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The plagal cadence (IV-I) provides a gentler conclusion than V-I and has more flexible voice leading conventions. Unlike the authentic cadence, there are no mandatory resolution tendency tones; all chord members can move by step or remain on common tones. The characteristic sound comes from the IV-I progression itself rather than from specific melodic resolutions. The plagal cadence often appears at the very end of a piece as the 'Amen' cadence.
Compare authentic and plagal cadence voice leading side by side to hear the different characters and recognize which resolution tendencies are unique to V-I versus those that apply generally.
From your prerequisite in cadence types, you know that the plagal cadence (IV-I) provides a gentler, more settling sense of closure than the authentic cadence (V-I). From your study of diatonic chords, you know the pitch content of IV and I in any key. The voice-leading dimension of the plagal cadence is distinctive precisely because it lacks the strong tendency tones that make authentic cadence voice leading so rule-governed — and understanding this difference is essential for writing and analyzing both cadence types correctly.
In an authentic cadence (V-I or V7-I), voice leading is tightly constrained by two powerful tendency tones. The leading tone (scale degree 7, the third of V) must resolve upward by half step to the tonic — this is nearly mandatory in four-voice writing. In V7, the chordal seventh (scale degree 4) must resolve downward by step. These two obligations are non-negotiable in strict style and define the characteristic sound of the authentic cadence: directed, urgent, decisive. The plagal cadence has none of this. The IV chord contains scale degrees 4, 6, and 1 — none of which function as leading tones or dissonant sevenths demanding specific resolution. Scale degree 4 can move down to 3 or up to 5; scale degree 6 can move down to 5 or up to 1 (via common tone); scale degree 1 is already a common tone with the I chord and can simply be held.
This flexibility is the plagal cadence's defining voice-leading characteristic. Where V-I has a specific, tight set of rules, IV-I offers multiple smooth paths to the tonic chord. The most common voicings hold the common tone (scale degree 1) while moving the other voices by step in whichever direction produces the smoothest motion. In C major, a typical four-voice plagal cadence might move F-A-C-F (IV) to E-G-C-E (I), with the soprano's F descending to E, the alto's A descending to G, the tenor's C holding, and the bass's F descending to E or C. But other configurations work equally well — the composer has genuine freedom to choose the most melodically satisfying motion in each voice.
The "Amen" quality of the plagal cadence — its gentle, settling character — comes directly from this absence of urgency. There is no leading tone pulling upward, no dissonant seventh needing downward resolution. The motion from IV to I is one of harmonic repose deepening rather than tension releasing. This is why the plagal cadence often appears after an authentic cadence, as a codetta or closing gesture: the V-I provides the definitive resolution, and the IV-I that follows adds a layer of peaceful confirmation, like the "Amen" that closes a hymn. In analysis and composition, the key takeaway is simple: do not apply V-I voice-leading rules to IV-I. The two cadences have fundamentally different voice-leading characters because they contain fundamentally different tendency-tone content, and respecting this difference is what allows each cadence to sound like itself.
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