The triad is a chord formed by stacking two thirds: a root, a third above it, and a fifth. Depending on which thirds (major or minor) are combined, the triad comes in four kinds: major (bright), minor (shaded), diminished (tense), and augmented (unstable, “expanded”).
The major and minor triads are the consonant support of all tonal music: on them are built the tonic, subdominant, and dominant. By rearranging the notes of a triad (inversions — the six-three and six-four chords), a composer changes its “weight” and colour without changing the harmony. The ability to hear and build triads is the first step toward understanding harmony; from these simple sonorities grows the whole multi-storey architecture of chords.
