A phrase begins in one sound and seems to continue in another. The change may be obvious, or it may happen while both overlap. Following that handoff is a useful way to listen to a busy arrangement.
Choose a short passage
Find a section where the sound carrying your attention changes. Note the moment and replay a little before it. Does the second part imitate the first, complete it, or begin a different idea?
If you cannot identify the instruments, describe their audible qualities: a sustained bright sound, a short plucked sound, or a low repeated figure. Keep the description provisional.
Listen for overlap
Notice whether the first part stops cleanly or remains underneath. In an illustrative sketch, one line can end as another starts; a second sketch can show the lines overlapping. These drawings need only represent your listening impression.
A change in prominence is not necessarily a change in the main melody. Avoid making a technical claim solely because one part suddenly becomes easier to hear.
Ask what stays recognisable
Perhaps a rhythm remains similar while the tone changes. Perhaps the contour is familiar but the phrase ends differently. Name one continuity and one difference.
Use drawing a melody’s shape if direction helps you follow the passage. The handoff gives you a small route through the music without needing to analyse the entire track at once.