How to Use Music Theory to Build Augmented Triads
You can use music theory to build augmented triads. Augmented triads are major triads that have had the fifth raised a half step, creating a slightly dissonant sound. An augmented triad is a stack of major thirds with four half steps between each interval.
You can build a C augmented triad (written as Caug) by counting out the half steps between intervals, like this:
Root position + 4 half steps + 4 half steps (8 half steps above root)
Here, you see C augmented on the keyboard.
Here is C augmented on the staff.
Using the method of starting with the major key signature first and then building the chord, the formula you want to remember for building augmented chords is
Augmented triad = 1 + 3 + sharp 5
So the first major scale degree and third major scale degree stay the same in the chord, but the fifth major scale degree is raised a half step.
It’s important to note here that sharp 5 doesn’t mean that the note will necessarily be a sharp. Instead, it means that the fifth note occurring in the scale degree is raised, or sharped, a half step.
Therefore, if someone asks you to write down an augmented F triad, you first write the key signature for F and then write your triad on the staff, using F as your root and raising the fifth position one half step.
If you were to build an A flat augmented triad, you would go through the same process and come up with a triad that looks like the one below. Note that the perfect fifth of A flat major is an E flat. Given A flat’s key signature, you have to “natural” the fifth to get to that E natural.