Have a listen here before you read further:
So what do we have? Two basic melodies. But I want to bring something to your attention. Check out the MIDI for the two melodies below. (They are in proper order.)
What do you notice about the ending of the first melody? It resolves back to where it started. That means it went all the way from an F… back to an F.
Try for yourself how it sounds, and you’ll notice it sounds “at rest” when you get back to the F3 note.But what happens if you end on another note, like D? It sounds more tense, or uneasy.
Now what happens in that second melody? The part in bar 2 flows well from the part before it. It has a similar shape — an upward slope. And notice that a new harmony is forming there. It’s as if we went from an F chord down to a Dm chord.
This observation is only useful if we can apply it in the future. So the next time you want to extend a melody, you can try ending on a different note, and then form a new shape to move the story forward.
Edit: There’ something special going on at the conclusion of the shorter melody. It’s like an inflection point. Of course there’s a lot of different places you could say that about.
Let me know in the comments if you hear what I’m talking about.