Theory & harmony
Triad
A triad is a three-note chord built from a root with a third and a fifth stacked above it, and it is the basic unit of western harmony.
The four types come from which thirds are stacked. Major is a major third then a minor third; minor is a minor third then a major; diminished stacks two minor thirds; augmented stacks two major thirds. Every one of the thousands of chords in common practice harmony is a triad with something added or altered.
Inversions rearrange which chord tone is lowest without changing the chord's identity: root position, first inversion with the third in the bass, second inversion with the fifth. Recognising an inverted triad on the page, the notes are no longer stacked neatly in thirds, is a specific skill worth practising deliberately.
Related terms
Every term in this glossary is taught in context somewhere in Arco's curricula, on the staff, on the keyboard, and on your own fingerboard at the same time.