Target/codes: compare circle-on-T/triangle-on-T′ with triangle-on-T/circle-on-T′ and explain what changed versus stayed; AC9AMUFD01, AC9AMUFC01. Prepare: E source board, two broad source icons.
- Welcome · 3 min. Fix T | T′ in a high-contrast frame; agree both scores will keep their rhythm marks.
- Model · 4 min. Swap only the circle and triangle source labels above the two complete phrases. Four-plus-four beat places and three planned events remain unchanged.
- Try together · 5 min. Child shows one unchanged rhythm cell and the two changed source labels. Do not call visual source labels proven acoustic timbres.
- Child choice · 7 min. Child selects an order of two abstract source cards for a paper robot or tactile picture, gives an intended sound contrast, or chooses the plain score. Optional reviewed sounds can be compared only if comfortable.
- Notice · 4 min. Record source order planned and what actual sound, if any, the child noticed. A generic PCM pitch change is not evidence of two instrument timbres.
- Close · 2 min. Save one version as a composing choice; tomorrow each learner can author both phrases.