Model B/C has no freeform per-note expression-text field at all — an agent cannot author dolce/espress./cantabile

Expressive text markings (dolce, espressivo, cantabile, semplice, etc.) are a standard, open-ended vocabulary distinct from the closed dynamic and technique vocabularies — a composer/arranger needs to attach arbitrary short italic text to a note.

Gould, Behind Bars, ch. Expression Marks — treats expression text as an open vocabulary (unlike dynamics), rendered in italic above the staff near the note it modifies; Ross, The Art of Music Engraving, agrees.

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