Goal
Identify and construct inversions, understand the harmonic stability of different inversions.
Inversions
Up until now when we made a triad the lowest note in the triad has always been the root note. This however doesn't need to be the case. The lowest note of the chord could easily be the 3rd or 5th. When the lowest note is not the root note the triad is said to be in an inversion.
Constructing triads in root position forms the "base form" of the triad. When we are identifying triads or constructing them we think of the root position version as its "base" form. Then we think of inversions as a variation of this base form.
Inversions are solely determined by the lowest note in the chord! The higher notes have no influence on the Inversion. In fact you could have many additional notes above the base note so long as they are all notes in the chord and still it is the same triad! Only changing the lowest note will actually change the Inversion!
Constructing Inversions
There are 3 possible notes that can be in the bass, the root, the third, and the 5th. When the root is in the base it's root position. When the third is in the base it's in the first Inversion. When the 5th is in the base it's in second inversion.
 | Root Position | Root Note (1st) |
 | 1st Inversion | 3rd |
 | 2nd Inversion | 5th |
Practice
Each inversion has harmonic properties. For this class we only need to know that the root position is the most stable, the first inversion is less stable and the third inversion is the least stable. We pick the one we want often based on how final we want to sound. Ending on a one chord in root position sounds much more final than ending on a 1 chord in 3rd inversion, which is why you may see this in the middle of a piece but certainly not at the very end!
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