Score order for SATB and larger ensembles

Vocal/chorale score order top-to-bottom is Soprano, Alto, Tenor, Bass — never any other order. For a full ensemble, standard top-to-bottom order (Gould, Read) is woodwinds, brass, percussion, harp/keyboard, (vocal soloists/choir), then strings at the bottom — Gradus does not yet need this since it has no multi-family ensemble content, but a future orchestration unit must follow it.

An SATB block where voice1/voice2/voice3/voice4 map to anything other than S/A/T/B top-to-bottom.

Gould (Behind Bars, standard full-score instrument order); Read (Music Notation, same ordering, near-universal with minor disagreement on harp/keyboard placement — Gould places it just above strings, some publishers place it just below brass; Gradus should follow Gould as the more current, widely adopted reference).

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