Diminished and Augmented Triads

These are the next two types of triads.

Augmented Triad

These are built on the root, Major third, and augmented fifth above the root. There are not any naturally occurring augmented triads in a Major key, which just means you'll need an accidental to use one. This chord is kind of unsettling and not very pleasant.

Diminished Triad

These chords are built on a root, minor third, and a diminished fifth above the root. There is only one naturally occurring triad in any Major key on the seventh degree. Diminished triads sound suspenseful.