Tonic base. Dually he considers the discharge 6-5 of the Subdominant agent into the Tonic associate. Both discharges are highly significant for key determination. The “DualDischarge”-Denotator of the Form PiMod₁₂DualSteps expresses this duality:

Function: Dominant - Subdominant. The initial inversion e⁷11 maps the G-Major-Triad onto the F-Minor-Triad and vice versa (see DualFunction₁), and it maps the G-Minor-Triad onto the F-Major-Triad and vice versa (see DualFunction₃). Furthermore it exchanges the G-“Dominant-Seventh-Chord and the F-Minor-Chord with added Sixth (see DualFunction₂).

Cadence: Authentic / Plagal. With respect to the functional dualism between Dominant and Subdominant and the modal dualism between the two Tonic variants as well as the two dominants there results a dualism between certain authentic and plagal cadences, namely those which differ modally in both chords:

Semicadences: These are obtained as retrograde versions of the cadence steps. It is clear that the resulting denotators fit into the PiMod₁₂DualSetSteps-Form. We omit the details. The inner symmetry of all four Dual-Forms makes clear, that it is not possible to formally decide upon what is left and what is right in Harrison’s table.

Alteration: Sharpen / Flatten. Harrison lists two corresponding pairs of alterations:

• the flattening of the 7th scale degree in C-Major B B_b together with the sharpening of the 6th scale degree A_b A in C-Minor. In modulations these alterations produce, for example, a 4th scale degree in F-Major and a 2nd scale degree in G-Minor, respectively. The alteration-pair as well as both resulting Scales are explained by suitable denotators Alteration₁ and DualAlteredScales₁.