RHY.2:4.1 - Start with the required discrimination

Ask what two possibilities must remain distinguishable. Examples are an entrance after the third rather than fourth attack, an accent produced by pressure rather than a break in contact, and a full rather than partial weight transfer.

Use the smallest material portion that contains the relevant relation. Extend it when the boundary matters: a cyclic pattern needs its return to the next cycle; an entrance may need the preceding cue; a continuous change may need more than its peak.