Introduction
Understanding triads and their qualities is one of the most essential skills you’ll need to master for AP Music Theory. Triads form the foundation of Western harmony, and being able to recognize, build, and analyze them is crucial for both the multiple-choice section and the free-response section of the exam.
This guide will walk you through everything you need to know about Major (M), minor (m), diminished (d), and Augmented (A) triads with full explanations, shortcuts, and helpful tips!
What Is a Triad?
A triad is a three-note chord consisting of:
- A root (the starting note)
- A third (either Major or minor)
- A fifth (either Perfect, diminished, or Augmented)
These three notes are stacked in thirds — meaning that each note is a third (either Major or minor) above the previous one.
The Four Triad Qualities
There are four basic triad qualities you must know:
| Triad Type | Structure | Example (Root C) | Sound Character |
|---|---|---|---|
| Major (M) | M3 + P5 | C – E – G | Bright, Happy |
| minor (m) | m3 + P5 | C – E♭ – G | Dark, Sad |
| diminished (d) | m3 + d5 | C – E♭ – G♭ | Tense, Unstable |
| Augmented (A) | M3 + A5 | C – E – G♯ | Dreamy, Unsettled |
Let’s break each one down carefully:
1. Major Triad (M)
- Formula: Root + Major 3rd + Perfect 5th
- Intervals from root:
- Major 3rd (4 half steps)
- Perfect 5th (7 half steps)
Example:
- Root = C
- Up a Major 3rd = E
- Up a Perfect 5th = G
Thus, C Major Triad = C – E – G.
Tip: Major triads sound bright, stable, and “happy.”
2. minor Triad (m)
- Formula: Root + minor 3rd + Perfect 5th
- Intervals from root:
- minor 3rd (3 half steps)
- Perfect 5th (7 half steps)
Example:
- Root = C
- Up a minor 3rd = E♭
- Up a Perfect 5th = G
Thus, C minor Triad = C – E♭ – G.
Tip: minor triads sound more somber, emotional, or “sad.”
3. diminished Triad (d)
- Formula: Root + minor 3rd + diminished 5th
- Intervals from root:
- minor 3rd (3 half steps)
- diminished 5th (6 half steps)
Example:
- Root = C
- Up a minor 3rd = E♭
- Up a diminished 5th = G♭
Thus, C diminished Triad = C – E♭ – G♭.
Tip: Diminished triads feel unstable and tense. They’re often used to create suspense before resolving.
4. Augmented Triad (A)
- Formula: Root + Major 3rd + Augmented 5th
- Intervals from root:
- Major 3rd (4 half steps)
- Augmented 5th (8 half steps)
Example:
- Root = C
- Up a Major 3rd = E
- Up an Augmented 5th = G♯
Thus, C Augmented Triad = C – E – G♯.
Tip: Augmented triads have a dreamy, mysterious, or floating sound and are less common in classical harmony but frequently appear in modern music.
How to Quickly Identify Triad Qualities
- Listen carefully: Major = happy, minor = sad, diminished = tense, augmented = dreamy.
- Check the intervals:
- Major = 4 half steps (M3), then 3 half steps (m3)
- minor = 3 half steps (m3), then 4 half steps (M3)
- diminished = 3 half steps + 3 half steps
- augmented = 4 half steps + 4 half steps
Shortcut Tip:
Think of it like stacking small or big building blocks! Two small blocks = diminished, two big blocks = augmented!
Triads in Key Signatures
Each diatonic scale (Major or minor) naturally produces certain triads on each scale degree.
Example: In C Major:
| Scale Degree | Triad | Quality |
|---|---|---|
| I | C – E – G | Major |
| ii | D – F – A | minor |
| iii | E – G – B | minor |
| IV | F – A – C | Major |
| V | G – B – D | Major |
| vi | A – C – E | minor |
| vii° | B – D – F | diminished |
You’ll be asked to recognize and write these triads in context on the AP exam, so practice building them in every key!
Final Thoughts
Triads are the building blocks of harmony in Western music. Mastering them will give you a huge advantage in AP Music Theory, especially for tasks like:
- Roman numeral analysis
- Figured bass realization
- Harmonic dictation
- Composition and part writing
Take time to practice identifying and building triads by hand and by ear every day — your musical instincts and theory skills will skyrocket!
Quick Practice Challenge 🎵
- Build a minor triad starting on G.
- Build a diminished triad starting on B♭.
- Build an Augmented triad starting on E.
(Scroll down for answers!)
Answers:
- G minor = G – B♭ – D
- B♭ diminished = B♭ – D♭ – F♭
- E Augmented = E – G♯ – B♯
AP Music Theory Quiz: Triads and Chord Qualities 🎶
Instructions: Choose the correct answer or fill in the blank. Answers are at the bottom!
1. What is the interval structure of a minor triad?
- A) Major 3rd + Perfect 5th
- B) minor 3rd + Perfect 5th
- C) minor 3rd + diminished 5th
- D) Major 3rd + Augmented 5th
2. Which of the following notes make up an F diminished triad?
- A) F – A – C
- B) F – A♭ – C♭
- C) F – A♭ – C
- D) F – A – C♯
3. A C Augmented triad consists of which three notes?
- A) C – E – G
- B) C – E♭ – G♭
- C) C – E – G♯
- D) C – D♯ – F♯
4. Fill in the blank:
The interval between the root and the fifth of a diminished triad is a ___________.
5. True or False:
A Major triad is built with a Major 3rd and a Perfect 5th above the root.
6. Build the triad:
Write the notes of an A minor triad:
✏️ Quiz Answers:
- B) minor 3rd + Perfect 5th
- B) F – A♭ – C♭
- C) C – E – G♯
- diminished 5th
- True
- A – C – E
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