Triads – Inversions

To review: There are four different qualities of triads – Major, minor, diminished, and augmented. They are shown below with their jazz/pop designations.

Each note of a triad has a name:

The root is the bottom-most note when the triad is built all in 3rds.
The third (3rd) is the note an interval of a third above the root.
The fifth (5th) is the note an interval of a fifth above the root.

Inversions

Any of the notes of the triad can be in the bass voice — the bottom-most voice.

If the root is in the bass (the bottom-most voice), the triad is in root position.

If the 3rd is in the bass, the triad is in first inversion.

If the 5th is in the bass, the triad is in second inversion.

Jazz/Pop designations

With jazz/pop symbols, all you have to do to indicate the inversion is indicate what note is in the bass. You do this by adding a / and the bass note.

The second chord above has the Ab (the 3rd of the triad) in the bass. Therefore we mark the chord as F-/Ab (F minor chord with Ab in the bass).

The third chord above has the C (the 5th of the triad) in the bass. Therefore, we mark the chord as F-/C (F minor chord with C in the bass).

If the root of the chord is in the bass (as in the first chord above), we just indicate the chord. We assume the root is in the bass unless otherwise designated.

Figured Bass

In classical music, we use a system called figured bass to indicate the inversion of the triad. Figured bass symbols are Arabic numerals that indicate intervals above the bass.

For root position chords, the figured bass contains 5 and 3 indicating intervals of a 3rd and 5th above the bass.

For a first inversion triad (i.e., the third is in the bass) chords, the figured bass contains 6and 3 indicating intervals of a 3rd and 6th above the bass.

For a second inversion triad (i.e., the fifth is in the bass) chords, the figured bass contains 6and 4 indicating intervals of a 4th and 6th above the bass.

Only the bass matters

We indicate the simple intervals in the figured bass; we assume the chord is written with the notes as close together as possible. This is not always the case, as seen in the examples below.

However, the inversion of the chord (and the symbols we use) are dependent on what note is in the bass (the bottom-most voice).

If the root is in the bass, the chord is in root position and the 5/3 designation is used.
If the 3rd is in the bass, the chord is in first inversion and the 6/3 designation is used.
If the 5th is in the bass, the chord is in second inversion and the 6/4 designation is used.

Remember, when using jazz/pop symbols, just indicate what note is in the bass. (See the indicators above the staff in the example above.)