Filling in the T–PD–D–T model. Add predominant chords (ii, IV) to a phrase, meet the tonic-substitute vi and the rare iii, resolve predominant seventh chords, and learn the special role of the cadential six-four and its neighboring, passing, and arpeggiated cousins.
Six ways to master Unit 5 — pick whichever fits how you like to study.
Seven topics from the College Board CED, in order.
Unit 5 fills out the predominant side of the T–PD–D–T model from Unit 4. You'll add IV/iv and ii/ii° to real phrases, meet vi as a tonic substitute (the target of the deceptive cadence), and see why iii is the rarest diatonic triad in this style. You'll also resolve predominant seventh chords (ii7, iiø7) and learn a new cadence type — the Phrygian half cadence.
The second half of the unit is the six-four chord: the famous cadential 6/4, which despite its spelling functions as a dominant embellishment rather than a tonic chord, plus the neighboring, passing, and arpeggiated six-fours that decorate a bass line without changing harmonic function.
Unlike most AP courses, the College Board does not assign a percentage of the exam to each unit — the exam is weighted by section (45% multiple choice, 45% free response, 10% sight-singing). But Units 4–7 (harmony and voice leading) drive most of the part-writing and analysis on the free-response section.
Unit 5 develops three of the four AP Music Theory Big Ideas: