Observing Melody

The question I should have asked yesterday is what order do they come from. Do they come before the music, or after?

If the music comes before, could it be that the person creating the melody only hears the possibilities that chord presents? I was wondering this, because when I hear a chord, I think of all the possible permutations of notes that can be sung with it. Like for example, I could choose any tone from a major scale to sing over a major chord, but I can also choose a Lydian mode, as it fits the chord as well. After all, a major chord is only three notes, and I would be adding a #11.

The natural extension of this is to take a chord progression, and make it work. Many chord progressions work with one parent scale too. Anyhow, the point is that this can be one way to create a melody. Chords first, melody second. This is very cool and worth messing around with, but what if the melody came first?

More on this tomorrow...