authentic cadence

The authentic cadence, also called a perfect cadence when both chords are in root position with the tonic in the soprano voice, is the most conclusive harmonic gesture in tonal music. The progression V–I (or V7–I) creates a powerful sense of arrival because the leading tone resolves upward to the tonic and the dominant bass note moves down a fifth to the tonic root, combining melodic and harmonic forces in a single gesture of resolution. A distinction is drawn between the perfect authentic cadence (PAC), where the melody ends on the tonic note over a root-position tonic chord, and the imperfect authentic cadence (IAC), where one or both chords may be inverted or the melody ends on a note other than the tonic. The PAC is the gold standard of finality in Western tonal music, and virtually every major composition from 1600 to 1900 ends with one.