Introduction to AP Music Theory Unit 3: Harmony & Voice Leading I
Unit 3 of AP Music Theory dives into harmonic function, chord progressions, and voice leading, forming the foundation for more advanced musical analysis. This unit is crucial for understanding how chords work together to create smooth, logical progressions in Western tonal music.
AP Music Theory Unit 3 Key Topics
Triad and chord Qualities (M,m,d,A)
Diatonic chords and Roman Numerals
Chord Inversions and figures: introduction to figured Bass
Seventh chord inversions and figures
1. Triads and Seventh Chords
Triads (Three-Note Chords)
A triad consists of:
- Root (the foundational note)
- Third (major or minor)
- Fifth (perfect, diminished, or augmented)
Types of Triads:
| Type | Formula (from root) | Example in C Major |
|---|---|---|
| Major | Root + M3 + P5 | C-E-G |
| Minor | Root + m3 + P5 | C-Eâ™-G |
| Diminished | Root + m3 + d5 | C-Eâ™-Gâ™ |
| Augmented | Root + M3 + A5 | C-E-G♯ |
Seventh Chords (Four-Note Chords)
A seventh chord adds a 7th above the root:
- Major 7th (M7) – Root + M3 + P5 + M7 (C-E-G-B)
- Dominant 7th (V7) – Root + M3 + P5 + m7 (C-E-G-Bâ™)
- Minor 7th (m7) – Root + m3 + P5 + m7 (C-Eâ™-G-Bâ™)
- Half-Diminished 7th (ø7) – Root + m3 + d5 + m7 (C-Eâ™-Gâ™-Bâ™)
- Fully Diminished 7th (°7) – Root + m3 + d5 + d7 (C-Eâ™-Gâ™-Bâ™â™)
2. Voice Leading Rules (Four-Part Writing – SATB)
Voice leading ensures smooth transitions between chords. The four voices are:
- Soprano (S) – Highest voice (melody)
- Alto (A) & Tenor (T) – Inner voices
- Bass (B) – Lowest voice (harmonic foundation)
Essential Rules:
✅ Avoid Parallel 5ths & 8ves – Two voices moving in the same direction to a perfect 5th or octave creates a weak sound.
✅ Resolve Leading Tones – The 7th of a V7 chord must resolve up by step.
✅ No Voice Crossing – Keep voices in their proper ranges (S > A > T > B).
✅ Common Tone Retention – Keep shared notes between chords in the same voice.
Example: Moving from V to I in C Major:
- V (G-B-D-F) → I (C-E-G-C)
- F (7th of V7) resolves to E (3rd of I)
3. Chord Progressions & Harmonic Function
Roman Numeral Analysis
Chords are labeled by their scale degree in uppercase (major) or lowercase (minor):
- I, ii, iii, IV, V, vi, vii° (in major)
- i, ii°, III, iv, V, VI, vii° (in minor)
Common Progressions:
- Authentic Cadence: V → I (strongest ending)
- Plagal Cadence: IV → I (“Amen” cadence)
- Half Cadence:Â Ends on V (creates tension)
- Deceptive Cadence: V → vi (surprise resolution)
Example in C Major:
- I – IV – V – I (Basic progression)
- ii – V – I (Common jazz/pop progression)
4. Cadences – Musical Punctuation
Cadences mark the end of a musical phrase:
| Cadence Type | Chord Progression | Effect |
|---|---|---|
| Authentic (Perfect) | V → I | Strong, conclusive |
| Plagal | IV → I | Soft, “Amen” ending |
| Half | Ends on V | Unfinished, expectant |
| Deceptive | V → vi | Surprise resolution |
Example:
- Perfect Authentic Cadence (PAC) in C Major: G (V) → C (I)
5. Practice Tips for AP Music Theory Unit 3
📌 Memorize Chord Qualities – Know major, minor, diminished, and augmented triads in all keys.
📌 Practice Four-Part Writing – Use SATB rules to write smooth progressions.
📌 Analyze Real Music – Study Bach chorales or Mozart piano pieces.
📌 Take Timed Quizzes – Use AP Classroom or Barron’s AP Music Theory for practice.
Final Thoughts
Unit 3 (Harmony & Voice Leading I) is essential for mastering chord progressions, cadences, and voice leading in AP Music Theory. By understanding Roman numeral analysis, four-part writing, and harmonic function, you’ll be well-prepared for the exam.
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