ANNOTATING HARMONY FOR NINTH CHORDS IN ROOT POSITION

The next figure shows how to annotate harmony for ninth chords in the root position.  The C major key and the A minor key are used. Thus, the assumption is that the chords in the figure are taken from passages written in these keys. The chords shown in the figure are in the root close position but the same annotations are also used for open positions. 

Figure: Annotating harmony for ninth chords in the root position

The G dominant ninth chord is annotated in the C major key as C: V9. The chord root G is the fifth scale degree of the C major key. Thus, it is annotated with the Roman numeral five. The interval between the chord root and chord third (G4 B4) is the major third. Thus, the Roman numeral is in the upper case.

The G dominant minor ninth chord is annotated in the C major key as C: Vb9. The chord root G is the fifth scale degree of the C major key. Thus, it is annotated with the Roman numeral five. The interval between the chord root and chord third (G4 B4) is the major third. Thus, the Roman numeral is in the upper case.

The C major ninth chord is annotated in the C major key as C: I∆9. The chord root C is the first scale degree of the C major key. Thus, it is annotated with the Roman numeral one. The interval between the chord root and chord third (C4 E4) is the major third. Thus, the Roman numeral is in the upper case.

The A minor ninth chord is annotated in the A minor key as a: i9. The chord root A is the first scale degree of the A minor key. Thus, it is annotated with the Roman numeral one. The interval between the chord root and chord third (A4 C5) is the minor third. Thus, the Roman numeral is in the lower case.