IV. Wing Structure
Wing
A subset of orbits sharing a characteristic interval coloring. The OTH analogue of major/minor modality.
d5-Wing
Orbits rich in tritones (diminished fifths): Q676 (Narrows), Q686 (Saddle), Q767 (Valley). Connected through the hub orbit Q776 (Upper Slope) to the core. Produces a darker, more dissonant harmonic color. The tritone is the least stable interval in Hindemith’s hierarchy.
A5-Wing
Orbits rich in augmented fifths: Q878 (Valley), Q788 (Precipice), Q688 (Precipice), Q868 (Valley). Connected through the hub orbit Q877 (Plateau) to the core. Produces a brighter, more expansive harmonic color. The augmented fifth (= minor sixth) is a relatively consonant interval.
Wing Color
The distinction between d5-wing and A5-wing harmonic character within a progression or passage. The OTH analogue of mode. A passage committed to one wing has a consistent harmonic color; crossing between wings creates mode mixture.
Hub Orbit
An orbit with high orbit-level connectivity that bridges a wing to the core. Q776 (Upper Slope, 5 orbit-level connections) bridges the d5-wing; Q877 (Plateau, 6 orbit-level connections) bridges the A5-wing.