The Basics of Music Theory - Part 5 (Triads and Inversions)

In the last installment of The Basics of Music Theory - Part 4, I covered the cycle of 4ths/5ths. This installment will begin the journey into the harmonic foundation of chords. The basic foundation of chordal theory is the triad. That is to say three (tri-) notes (-ads). 

The Building of Triads

A triad is a chord containing three notes (as said earlier). It is built using the 1st, 3rd, and 5th degree of a given scale. After determining the initial triad from the major scale, we can then change its qualities to create different types. We can either lower the 3rd (b3) or 5th (b5) scale degrees by a half step or raise the 5th (#5) scale degree by a half step. Below is a table showing the different changes that can be made to create each type. Notice that the root note of the triad does not change and the other notes move by half step to create a new version of the original chord.

Triad Type Scale Degrees
Major (Maj) 1 3 5
Minor (min) 1 b3 5
Diminished (dim) 1 b3 b5
Augmented (aug) 1 3 #5

Understanding Triad Inversions

Each triad listed above can be played in generally three different ways. It all depends on which note is the lowest sounding. For example, a C Major chord is made up of the three notes C - E - G. When the root, C, is the lowest sounding it is in root position. When the 3rd degree, E, is the lowest sounding, then it is in 1st inversion. When the 5th degree, G, is the lowest sounding, then it is in 2nd inversion.

If you look at the example below, then you can see each inversion for the four types of triads listed above. These, of course, are all based on the C root note.


I hope you are enjoying the series on theory. Next we will look at using this knowledge to create diatonic triads (if you don't know what that means your are in the right place!). If you missed anything from before, then follow this link (The Basics of Music Theory - Part 4 (Cycle of 4ths)) to the previous part of this series.

FYI: I mentioned this before for those of you interested in a much deeper level of theory study on the guitar, check out: Music Theory for Guitarists: Everything You Ever Wanted to Know But Were Afraid to Ask. Tom Kolb does a great job explaining the ins and outs. It also includes access to online audio access.

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