If you’re interested in learning more about the classification of triads, then you’re on the right page.
There are four common triads in traditional harmony:
The major triad
The minor triad
The diminished triad
The augmented triad
…and there are more than one theoretical basis for the classification of these triads. But in this lesson, we’re focusing on the concept of stability and how it can be used in the classification of triads.
Kindly give me your undivided attention and the next seven minutes and guarantee you that your perspective to major, minor, diminished, and augmented triads will change.
The Concept Of Stability — Explained
When a chord is played, the outcome is either agreeable (stable) or not.
Agreeable (or stable) chords are classified as concord while chords that have a degree of tension (and having the tendency to move to a more stable chord when played) are classified as discord.
Before we take a look at the discord, let’s talk about the concord.
Quick Insights On The Concept Of The Concord
Chords that are ONLY made up of consonant intervals are classified as concord.
The following intervals are consonant:
The minor third
The major third
The major sixth
The minor sixth
The perfect fifth
The perfect octave
…and chords with these intervals are said to be concordant.
A Short Note On The Concept Of The Discord
The primary source of discord are chromatic dissonant intervals. Once a chord has one or more chromatic dissonant intervals as its component, such a chord will sound unstable.
Here’s an example:
In the C dominant seventh chord:
…the interval between the 3rd and 7th tones (which are E and Bb respectively):
…is a diminished fifth interval — which is a chromatic dissonant interval. It is the chromatic dissonant interval (E-Bb) in the C dominant seventh chord that makes it discordant.
It is also important to note that following intervals are dissonant:
All augmented intervals
All diminished intervals
The minor second
The major second
The perfect fourth
The minor seventh
The major seventh
…and any chord with any of the above-mentioned intervals are classified as discord.
The Classification Of Triads According To Stability
Let’s go ahead and classify the four commonly known triads:
The major triad
The minor triad
The diminished triad
The augmented triad
…according to stability. Don’t forget that the stability of a chord is determined by its intervallic components. So, we’ll be looking out for consonant and dissonant intervals.
The Major Triad
The C major triad (our reference) can be broken down into the following intervallic components:
C to E:
…a major third interval.E to G:
…a minor third interval.C to G:
…a perfect fifth interval.
All the intervals in the major triad are consonant; consequently, the major triad is a stable triad. So, all major triads are classified as stable chords.
The Minor Triad
A breakdown of the C minor triad:
…shows the following intervallic components:
C to Eb:
…a minor third interval.Eb to G:
…a major third interval.C to G:
…a perfect fifth interval.
The minor third, major third, and perfect fifth intervals derived from the minor triad are ALL consonant intervals and this makes the minor triad a stable triad (just like the major triad).
The Diminished Triad
The diminished triad consists of the following intervals: the minor third and diminished fifth interval. Using the C diminished triad (as a reference):
…here are the intervallic components of the diminished triad:
C to Eb:
…a minor third interval.Eb to Gb:
…a minor third interval.C to Gb:
…a diminished fifth interval.
The diminished triad has a diminished fifth interval and it’s important to note that the quality of the triad (which is diminished) is derived from the diminished fifth interval.
Attention: In the previous segment, we learned that chords that have diminished intervals (which are dissonant) are classified as discord.
The diminished triad (because of the diminished fifth interval it consists of) is not a stable triad; it’s rather said to be active. When an active triad is played, the dissonance between chord tones create the tendency for the triad to move (or resolve) to a more stable chord.
In a nutshell, the diminished triad is an active triad.
The Augmented Triad
The C augmented triad (our reference) can be broken down into the following intervallic components:
C to E:
…a major third interval.E to G#:
…a major third interval.C to G#:
…an augmented fifth interval.
The augmented triad (because of the augmented fifth interval) is NOT a stable chord. So, it is classified as an active triad.
Final Words
In the classification of triads according to stability, there are basically two classes of triads: stable and active triads.
Stable Triads
The major and minor triads are stable triads and this is because of the absence of dissonant intervals. Major and minor triads can be broken down to the following consonant intervals:
The major third
The minor third
The perfect fifth
Active Triads
Diminished and augmented triads are active triads and when played they have the tendency to move to a more stable chord. The active triads (the diminished and augmented) have the following dissonant intervals:
The diminished fifth
The augmented fifth
See you in the next lesson!
