Cadences · The chords of a key · Music theory
A cadence is the ending of a phrase or a section, and it is recognized by its last two chords. Five are asked about in exams.
Cadences
A cadence is the ending of a phrase or a section, and it is recognized by its last two chords. Five are asked about in exams.
The perfect authentic cadence is V – I, both in root position and with the tonic in the highest voice: the most conclusive ending. The imperfect authentic cadence is also V – I, but with a chord inverted or without the tonic on top. The plagal cadence is IV – I, the “amen” of hymns. The half cadence ends on V, like a question. The deceptive cadence is V – VI, which fools the ear when it expected I.
What Piston says about the authentic cadence
Piston considers cadential formulas the most important of all, because they mark the breathing points, confirm the key and give coherence to the form. And he notes that they kept their validity throughout the common-practice period.
The V–I formula is extended with the chords that prepare it: II or IV before it, and the cadential six-four to announce it. So II⁶–I⁶₄–V–I or IV–I⁶₄–V–I are very strong. For Piston, the perfect cadence requires dominant and tonic in root position and the tonic in the soprano at the end; with the 3rd in the soprano or with V inverted, it is less conclusive.
Other cadences worth knowing
The Phrygian cadence is a half cadence of the minor mode: IV⁶–V, with the bass falling a half step, from F to E in A minor. It has a very characteristic flavor and is common in Baroque music.
Cadences are also grouped by effect: conclusive, those that can end a work (perfect authentic, plagal), and suspensive, those that leave the phrase open (half, deceptive). The plagal often appears as a confirmation after a perfect cadence, as a calm close.