Diminished and Augmented Triads

Symmetrical Triads — Diminished and Augmented

A diminished triad is built from two stacked minor thirds (m3 + m3), producing root + m3 + b5 (e.g. C-Eb-Gb).

An augmented triad is built from two stacked major thirds (M3 + M3), producing root + M3 + #5 (e.g. C-E-G#).

Diminished triads sound tense and unstable — they want to resolve inward. Augmented triads sound expansive and unresolved — they want to resolve outward.

Both are symmetrical structures, which gives them a restless, ambiguous quality that composers use to create tension before resolution.

C Major, Diminished, and Augmented

Study the progression from C major to Cdim to Caug. Observe how each triad type has a distinct emotional color: stable (major), tense (diminished), expansive (augmented).

Play Diminished and Augmented Triads

• Play each triad and identify its quality by sound alone
• Notice how diminished triads create inward tension
• Notice how augmented triads create outward expansion
• Compare each to the major triad on the same root