A cadence is a point of arrival that occurs at the end of a phrase. Two harmonies make up a cadence, the second chord being the point of arrival.
The type of cadence heavily influences the flow of music. Cadences can be used to momentarily interrupt the flow, create expectation that the flow will continue, thwart expectations of where the flow is going, or stop the flow entirely.
Finding cadences can sometimes be a little tricky. Listening to the music is the best method for locating points of arrival and closure. Tracking the melody or most prominent musical line is helpful in defining the structure of a phrase.
The type of cadence is defined by the voice leading in the bass and soprano and/or the harmonies involved in the cadential progression. To find and analyze a cadence, follow these instructions:
The PAC is the most conclusive of all the cadences, it is commonly used to bring finality and closure to the end of phrases, sections, and entire pieces.
The leading tone, scale degree ^7, is raised in the minor key to provide half-step resolution to the tonic and make the dominant a major chord.
The IAC is not as conclusive as the PAC. It provides a similar sense of tonal stability but also implies that the musical momentum will continue to a final PAC.
If either the dominant or tonic are inverted, the cadence is imperfect, regardless of the soprano’s voice leading.
Any cadence that moves from dominant to tonic is generically referred to as an authentic cadence. The particular voice leading and bass motion determines if the authentic cadence is perfect or imperfect.
The half cadence is typically followed by a tonic chord after a rest. The longer the pause, the stronger the expectation for resolution to tonic. Some pieces actually end on a HC!
In common practice music, the plagal cadence is usually written after an authentic cadence, as seen here. In the mid to late 19th century, plagal cadences are sometimes used in place of authentic cadences to shift the emphasis away from the dominant and create tonal ambiguity.
As the name implies, the deceptive cadence tricks the listener with a submediant resolution instead of the expected tonic. The sense of surprise is effective because of the strong expectation for the dominant to resolve.
The deceptive cadence works equally well in the minor mode.
The third of this chord has been doubled. If the tenor moved from B to C-sharp, there would be parallel fifths between the tenor and bass. And if the tenor moved from B to F, doubling the bass, this would create a tritone leap. The G-sharp in the soprano must resolve up by step since it is a tendency tone. In this case, doubling the third in the tenor is a good voice-leading option considering the alternatives.