VI. Progression & Motion Terminology
Ascent
A degree-ascending progression (from lower to higher degree). The “strong” direction in OTH grammar. An ascent from Saddle to Summit is the OTH cadence.
Descent
A degree-descending progression (from higher to lower degree). The “weak” direction — departure from stability toward tension. A descent from Summit to Saddle sets up a cadence.
Traverse
A progression that stays within the same degree level, moving laterally through B. Traverses provide harmonic variety without changing tension level.
Window Slide
Transposition of an entire chord by semitone (or by any interval), moving between different key regions of B. The OTH analogue of modulation. Geodesic distance 4 in B. The 12 Summit chords connected by T₁ transposition form the window-slide cycle — the 12 keys of OTH.
OTH Cadence
The progression Saddle → Slope → Summit ([6,8,6] → [6,7,7] or [6,8,7] → [7,7,7]). The fundamental resolution formula. The voice motion involves two single-semitone steps, each widening a tritone (d5→P5) or contracting an augmented fifth (A5→P5).
OTH Departure
The progression Summit → Plateau → Slope → Saddle. The fundamental tension-building formula.
Leading-Interval-Pair
The two coordinated semitone resolutions at the cadential moment — both voices moving simultaneously to convert the Saddle’s d5 intervals into the Summit’s P5 intervals. The OTH analogue of the leading tone’s resolution.