Augmented triad

Two major thirds

The learning path Chords sums up the four types of triad like this: a triad arises when you stack two thirds on a root. In major the major third lies at the bottom, in minor the minor; in the diminished triad two minor thirds lie on top of each other and in the augmented two major ones. Major and minor have a perfect fifth and sound stable. Diminished and augmented sound unstable because their fifth is narrowed or widened, and ask for resolution.

The semitone numbers correspond to the table in the ear training Identify Chords.

Structure in notes

Without a root

Because both thirds are equally large, the chord divides the octave into three equal sections of four semitones each. C–E–G♯–C is the series of notes in which every note has the same distance from the next. Such a chord has no “up” or “down” for the ear to hold on to, and that is why it is hard to assign to a key. The Chords page calls it “floating, hard to place”.

Sound and ear training

The comparison shows how little it takes: from C major to C+ only the fifth changes, G becomes G♯. The ear training puts major and minor first and adds diminished and augmented only afterwards. The advice there holds here too: listen specifically to the top note instead of the overall impression, and sing the root along before you decide.

Where it occurs

In a major key no augmented triad lies on any of the seven degrees. In minor it arises in harmonic minor on the third degree when the leading tone is raised. In A minor that is C+ from C–E–G♯; the table on the page A minor lists it in the harmonic-minor column as augmented. It is related to the major triad shown in the natural-minor column by exactly one note.