Augmented and Diminished Triads
Updated: May 1, 2019
We've talked about building major and minor triads and the intervals within each of the three notes used to create them. To make a major or minor triad, the interval quality between the root note and the top note needs to be a perfect fifth. The only interval quality that changes is between the root and third, as well as the third and 5th. It's important to note that I'm also specifying that the quality of the interval is changing and not the type. When we change the interval quality from the root to the 5th, we can create augmented or diminished triads depending on whether we raise or lower the 5th by a half step.
To create a major triad, we must add a major third and a minor third interval together. This gives us seven total steps, which makes a perfect fifth from the root note to the top note of the triad. To change a major triad to an augmented triad, we raise the 5th half of a step, making a total of eight half steps from the root. When it comes to interval quality, we can never have a minor or major 5th interval, only perfect, augmented or diminished.
To create a minor triad, we must add a minor third and a major third interval together. Note that the interval quality is still perfect between the root and fifth with a minor triad. We've just switched the interval types around and made the interval quality minor first between the root and 3rd, and major between the 3rd and 5th. To change a minor triad to a diminished triad, we lower the 5th by a half of a step, making a total of 6 half steps from the root.