Like intervals, triads vary in the quality of their sound, depending on the specific thirds used in their construction. The terms used to designate triads are major, minor, diminished and augmented. As with intervals, we can use uppercase and lowercase abbreviations to refer to the quality of the triad.
It is important you learn the four types of triads and understand how they are constructed. In each case, it is the quality of the third above the root and the quality of the fifth above the root that determine the overall quality of the triad.
Here is a diagram that summarizes how the four qualities of triads are built. The bottom row represents the quality of the 3rd created by the root and chordal 3rd. The middle row represents the quality of the 3rd created by the 3rd and 5th of the triad.
Quickly being able to recognize and write major 3rds, minor 3rds, and all 5ths will obviously help with this lesson since those are the intervals used to construct triads. The following examples show the thirds that are minor, followed by the thirds that are major. Notice the similarity with the order of flats in a key signature (B E A D / G C F)! If you learn to recognize these thirds instantly, your life will be much easier when dealing with triads.
- Natural thirds built on B, E, A, and D are minor.
(With one natural half step, they each have 3 half steps on the piano keyboard.)
- Natural thirds built on G, C, and F are major.
(With no natural half steps, they each have 4 half steps on the piano keyboard).
- Also, remember that all natural 5ths are perfect except B-F (which is diminished).
Some students find it helpful to memorize the qualities of the “natural” triads; that is, those without accidentals. Notice that the roots follow the order of flats in key signatures.
If the natural triads are memorized, then you can quickly determine the types of thirds and fifths involved and add accidentals as necessary when writing triads. You can also determine how accidentals change the size of thirds and fifths when determining the quality of triads.
Introduction to triads
Natural 3rds and Triads
Major and Minor Triads
The ‘B’ Triad