Augmented Triad

Triad Major Triad Diminished Seventh Whole Tone Scale Chromatic Scale

The augmented triad is the odd one out among the four triads: two major thirds stacked.

C–E–G♯: C to E is a major third, and E to G♯ is a major third again

It has two properties the others lack:

Property	Explanation
Root to fifth is an augmented fifth	Not perfect and not diminished — it is a semitone wider than perfect
The structure is perfectly symmetrical	Every span is a major third, so any of the three notes can serve as the root

Two consequences of the symmetry

One: there are only four of them. The structure repeats every four semitones, so scales starting on C, C♯, D and D♯ cover everything; the rest are repeats (enharmonic equivalents). It is the same logic as the diminished seventh — both are symmetrical structures that divide the octave equally.

Two: it has no direction. The function of a triad comes from knowing which note is the root and where the chord is heading. Here the three notes are equals and any of them can be heard as the root — so the sense of belonging disappears.

It does not occur in any diatonic scale

As noted earlier, the seven triads of a major scale run: three major, three minor, one diminished, zero augmented. The augmented triad never appears diatonically; it requires chromatic alteration.

Which is why its typical uses are all unsettled ones:

Transitions: sliding from one harmonic area to another without landing on a stable chord;
Chromatic motion: all three notes move a semitone in the same direction, giving a block-slide effect;
Suspension: held as a sustained harmony where hovering is the point (common in Impressionism and film

scoring).

Diagram: two symmetrical structures

Listen: the augmented triad

As you listen, try to decide which note is the root — you will not be able to. That is both its character and the reason it works only as a transition.

Common misconceptions

"An augmented triad is a major triad with a sharp added." It is a major third plus another major third; root to fifth is an augmented fifth, no longer perfect.
"It is common in music." It appears in no diatonic scale and requires chromatic alteration, so it is far rarer than major and minor triads.
"Inversion changes the root." Because the structure is symmetrical, inversions *sound* like different chords, yet in notation the root stays put. This is where the ear is most easily fooled.
"Symmetry should sound more stable." The opposite. Stability comes from unequal distances; equidistant structures (augmented triad, diminished seventh, whole-tone scale) offer no sense of belonging.

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Listen in the library

Scales, Arpeggios, and CadencesC13:22Scale exercises can sound an augmented-triad arpeggio, useful for hearing its lack of directionDetailsScriabin: Piano Sonata No. 10, Op. 70C112:53A late Scriabin sonata — its harmony rests on symmetrical pitch collections of his own design, a useful parallelDetailsDanse Macabre, S.555C110:20Liszt's transcription of Danse macabre — chromatic writing often throws up augmented sonorities, hear them used as transitionsDetails

All tracks from midicn-lib — inline badge is the license tier (C1 commercial / C2 non-commercial / C3 study only).

Sources

增三和弦 = 大三度 + 大三度，根音到五音为增五度，属和声学通则
增三和弦因结构对称而只有四个不同形态（互为等音），为通行和声学表述

Used for fact-checking only; all prose is original.

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