Where chords start behaving like harmony. How chords function (tonic, predominant, dominant), the cadences that punctuate phrases, phrase and period structure, and the four-voice (SATB) voice-leading rules that keep part-writing clean — including how to resolve seventh chords.
Six ways to master Unit 4 — pick whichever fits how you like to study.
Five topics from the College Board CED, in order.
Unit 4 is where chords become harmony. Instead of just spelling chords, you'll see how they function — tonic chords feel like home, predominant chords set up the dominant, and dominant chords pull back to tonic. Progressions move through this cycle and land on cadences, the harmonic punctuation that ends a phrase.
You'll also start four-part (SATB) writing: connecting chords with smooth voice leading, avoiding parallel fifths and octaves, doubling and spacing voices correctly, and resolving tendency tones — the leading tone up to tonic and the chordal seventh down by step.
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, so this unit is heavily represented on the free-response section.
Unit 4 develops three of the four AP Music Theory Big Ideas: