Cadence (music)

In Western musical theory a cadence is a particular series of chordss that ends a phrase, section, or piece of music. Cadences give phrases a distinctive ending, that can, for example, indicate to the listener whether the piece is to be continued or concluded. An analogy can be made with punctuation, with some weaker cadences acting as commas, indicating a pause or momentary rest, while a stronger cadence will then act as the period, indicating the end of the phrase or musical sentence. Cadences are called "weak" or "strong" the more or less final the sensation they create, with the perfect authentic cadence being the strongest type.

In music of the common practice period, there are four main types of cadences: authentic (perfect and imperfect), plagal (perfect and imperfect), half, and deceptive. Each of these types can be further distinguished as perfect or imperfect. Each cadence can be described using the roman numeral system of naming triads (see chord):

Authentic cadence: V to I. The phrase perfect cadence is sometimes used as a synonym fro authentic cadence, but can also have a more precise meaning:
- Perfect authentic cadences: V to I, the chords must be in root position, that is the root of the chords must be in the bass, and the root of I must be in the highest voice also
- Imperfect authentic cadences: V to I, one or more of the chords are inverted or not in root position or the root of the I is not in the highest voice
Half (or imperfect) cadence: any chord (frequently I or IV) to V
Plagal sequence: IV to I, known as the "Amen cadence"
Deceptive (or interrupted) cadence: V to any chord except I (typically vi)

It should be noted that these chord sequences do not necessarily constitute a cadence - there must be a sense of closure, as at the end of a phrase. Early music cadences, for instance, are different and more varied.