Tritone outlining (melodic and implied)

A melodic line tracing the shape of a tritone across a short span — a single direct leap, or two consecutive same-direction leaps whose combined net motion spans a tritone with no intervening stepwise motion — is forbidden by Fux/Jeppesen. A single intervening STEP between the outer notes removes the fault, since the ear then hears a scale fragment rather than a bare leap-defined tritone.

F4 → (leap) → B4 directly, or F4 → A4 (3rd) → B4 (3rd, same direction) with no stepwise note filling the gap — both outline the tritone F-B unresolved.

Fux (Gradus ad Parnassum) via Jeppesen's codification of species melodic prohibitions.

This rule can be decided from pitches, durations and voices — no layout required. A validator can check it before anything is drawn.