Augmented triad

An augmented triad is a three-note chord built from two stacked major thirds, producing a major third and an augmented fifth above the root (e.g., C–E–G♯). On the AP Music Theory exam, it's one of the four triad qualities (M, m, d, A) you must identify by ear and in notation.

What is the Augmented triad?

An augmented triad is one of the four triad qualities in AP Music Theory. Like every triad, it's three distinct pitches stacked in thirds (PIT-1.O.1). What makes it augmented is the recipe. You take a major third, then stack another major third on top. That gives you a major third and an augmented fifth above the root. C–E–G♯ is the classic example. Compare that to a major triad (C–E–G), where the top interval is only a minor third.

Because both of its thirds are the same size, the augmented triad is perfectly symmetrical. It splits the octave into three equal major thirds, which is exactly why it sounds so unstable and unresolved. There's no perfect fifth anchoring it, so your ear can't settle on which note is 'home.' That bright, tense, slightly eerie quality is your aural fingerprint for it on listening questions. It's also why composers use it for dramatic tension, and why it shows up in chromatic contexts like tonicization through secondary leading-tone harmony.

Why the Augmented triad matters in AP Music Theory

The augmented triad lives in Unit 3 (Music Fundamentals III: Triads and Seventh Chords), specifically Topic 3.1, Triad and Chord Qualities (M, m, d, A). It directly supports learning objective 3.1.A, which asks you to describe the quality of a chord in both performed music and notated music. In plain terms, you have to do two things with this chord. First, hear it and label it 'augmented' on aural questions. Second, see it on a staff (or spell it yourself) and identify the quality from the intervals. Augmented is the rarest of the four qualities in real diatonic music, which actually makes it easier to test. If a triad doesn't fit the familiar major, minor, or diminished sound, augmented is often the answer, and the exam expects you to confirm that by checking the intervals, not by guessing.

How the Augmented triad connects across the course

Major triad (Unit 3)

An augmented triad is a major triad with the fifth pushed up a half step. C–E–G becomes C–E–G♯. That one-note change is the fastest way to spell augmented triads on the exam, and it's why the two can sound related at first hearing before the augmented fifth gives it away.

Diminished triad (Unit 3)

Diminished is the mirror image of augmented. Diminished stacks two minor thirds (small + small), augmented stacks two major thirds (big + big). Both lack a perfect fifth, so both sound unstable, but diminished sounds tight and crunchy while augmented sounds stretched and bright.

Secondary leading tone chord (Units 5+)

Augmented sonorities show up when music tonicizes other keys with chromatic chords. Knowing how altered fifths change a chord's quality in Unit 3 is the groundwork for analyzing these secondary chromatic harmonies later in the course.

Voice-Leading Rules (Unit 4)

Unstable chords create tendency tones. The raised fifth of an augmented triad (like G♯ in C–E–G♯) wants to resolve upward by half step, the same logic that governs leading tones in part-writing. Quality identification in Unit 3 feeds directly into resolution decisions in Unit 4.

Is the Augmented triad on the AP Music Theory exam?

Triad quality is tested two ways, matching LO 3.1.A. Aurally, you'll hear a triad (blocked or arpeggiated) and pick its quality from M, m, d, and A. Visually, you'll see a notated triad and identify the quality from its intervals, or you'll be asked which intervals define each quality. Practice questions hit this head-on with stems like 'Which triad has a major third and augmented fifth?' so memorize the interval recipe cold. You may also see comparison questions, like how an augmented triad affects harmonic tension compared to a major triad (the answer hinges on its instability and lack of a perfect fifth). Watch for enharmonic traps in notation. G♯ above C makes the triad augmented; A♭ spelled in its place is a different interval entirely, and quality is determined by spelling, not just sound.

The Augmented triad vs Diminished triad

Both are the 'altered' triad qualities without a perfect fifth, so they get mixed up on interval-recipe questions. Keep it simple. Diminished = minor third + diminished fifth above the root (two stacked minor thirds, the chord shrinks). Augmented = major third + augmented fifth above the root (two stacked major thirds, the chord stretches). Aurally, diminished sounds dark and pinched; augmented sounds bright and unresolved. If an MCQ says 'minor third and diminished fifth,' that's diminished, not augmented.

Key things to remember about the Augmented triad

• An augmented triad is built from two stacked major thirds, giving it a major third and an augmented fifth above the root, like C–E–G♯.

• It's one of the four triad qualities (major, minor, diminished, augmented) you must identify by ear and in notation under learning objective 3.1.A in Topic 3.1.

• The easiest way to spell one is to build a major triad and raise the fifth a half step.

• Because it divides the octave into three equal major thirds, the augmented triad has no perfect fifth and sounds unstable, which is why it creates harmonic tension compared to a major triad.

• Don't confuse it with the diminished triad, which stacks two minor thirds and has a diminished fifth instead of an augmented one.

• Quality depends on spelling, so an enharmonically respelled note (G♯ vs. A♭) can change whether a chord is actually augmented.

Frequently asked questions about the Augmented triad

What is an augmented triad in AP Music Theory?

It's a triad made of two stacked major thirds, creating a major third and an augmented fifth above the root (C–E–G♯). It's one of the four chord qualities, abbreviated A or +, tested in Unit 3 Topic 3.1.

How is an augmented triad different from a diminished triad?

They're opposites. Augmented stacks two major thirds for a major third plus augmented fifth; diminished stacks two minor thirds for a minor third plus diminished fifth. Augmented sounds bright and stretched, diminished sounds dark and compressed.

Is an augmented triad just a major triad with a sharp?

Mostly yes, and that's a useful shortcut. Take any major triad and raise the fifth by a half step (C–E–G becomes C–E–G♯) and you get an augmented triad. The root and third stay the same; only the fifth changes.

Does an augmented triad occur naturally in a major scale?

No. In a major key, the diatonic triads are major, minor, and diminished only. The augmented triad appears diatonically on the third scale degree of harmonic and melodic minor, and otherwise requires chromatic alteration, which is why it signals tension and tonicization.

How do I hear an augmented triad on the AP exam?

Listen for a bright, unresolved, almost floating sound with no stable fifth. If a triad sounds neither settled like major nor sad like minor nor crunchy like diminished, check augmented. Its perfect symmetry means no note feels like home.