Cadence

In Western musical theory, a cadence is a structural tool used to end a musical phrase. It uses melody or harmony to create a sense of resolution. This resolution can feel complete or only partial. Music historians often view cadences as vital markers of musical meaning. The musicologist Edward Lowinsky even called the cadence the "cradle of tonality." This suggests that cadences are the foundation for how tonal music functions.

There are two primary ways to classify a cadence: harmonic and rhythmic. A harmonic cadence is a progression of two or more chords. This sequence concludes a phrase, a section, or an entire piece. A rhythmic cadence uses a specific pattern to indicate an ending. Musicians also label cadences as "weak" or "strong." This label depends on the impression of finality they give the listener. The harmonic rhythm, or the rate at which chords change, helps determine where a cadence occurs.

Music theorists divide harmonic cadences into four main types. These are the authentic, half, plagal, and deceptive cadences. Authentic cadences move from a dominant-functioning chord to a tonic chord. The tonic is the central pitch of a piece. A perfect authentic cadence (PAC) is the strongest version. In a PAC, the chords are in root position. This means the roots of both chords are in the bass. Also, the tonic must be in the highest voice.

Imperfect authentic cadences (IAC) offer variations of this strong sound. One type is the root position IAC, where the highest voice is not the tonic. Another is the inverted IAC, where one or both chords are inverted. There is also the leading-tone IAC, which replaces the penultimate chord with a leading-tone triad. A specific subtype is the evaded cadence. This occurs when a dominant seventh chord moves to a first inversion tonic chord. This movement happens because the seventh must fall stepwise to the tonic's third.

A half cadence, or semicadence, ends on a dominant chord (V). Because it does not reach the tonic, it sounds incomplete. This creates a "weak" feeling that calls for more music. There are several specific versions of the half cadence. The Phrygian half cadence uses a iv6–V progression in a minor key. It has an archaic sound from the Renaissance era. The Lydian half cadence is similar but uses a raised fourth. There is also the rare plagal half cadence, which uses a I–IV progression.

The plagal cadence moves from the subdominant (IV) to the tonic (I). It is famously known as the "Amen" cadence. This is because it is frequently used in hymns. Some musicians use a minor plagal cadence for a strong resolution. Another unique form is the Moravian cadence. This occurs when the outer notes of the first chord move inward by a tone. This specific type appears in the works of composers like Leoš Janáček.

A deceptive cadence, also called an interrupted cadence, is a surprising move. It moves from a dominant chord to something other than the tonic. Most often, it moves to the submediant chord (VI). This creates a "hanging" or suspended feeling for the listener. Gustav Mahler used many deceptive cadences at the start of his 9th Symphony. Brahms also used this in his Third Symphony to sidestep between keys. Even popular music, such as Pink Floyd, uses this technique.

Cadences can also be categorized by their rhythmic position. A metrically accented cadence ends on a strong beat, like a downbeat. These are considered structurally significant. A metrically unaccented cadence ends on a weak beat. This can make the resolution feel less forceful. Finally, the Picardy third is a special Renaissance device. It involves ending a minor or modal section with a major tonic chord. This provides a bright, unexpected sense of closure to a dark passage.