What is the relationship between the melody line and the rhythm chords?

Question

Let's say I've written a song with the chord progression I-IV-V in the key of A (just as an example). So, the chords I'm playing are A-D-E. When playing a lead over this rhythm, what notes do I need to stick to over each chord? That is, when playing an A chord, should I stick to the notes that compose the chord? Are there rules for which notes sound good over which chords? When I move to D, are there notes I should avoid or continue?

Answer 1

You don't really need to "stick to" anything. Chord tones in a melody will always bring the melody into focus with the harmonic background, while non-chord tones may function as passing tones as you move from one chord tone to another, as added color tones, as deliberate dissonances that add tensions and later resolve to consonances (usually chord tones), or even non-chord tones that deliberately avoid both chord tones and the even the underlying key.

Learning how to use all these possibilities is a big part of learning to compose music.

Answer 2

Most melodies will have a combination of chord tones (notes that are members of whatever chord is being played under the melody) and non-chord tones (notes that are not). Often they'll be part of a scale; since members of a chord are a 3rd or a 4th apart, every other note in a scale will probably be a chord tone. Imagine playing A-B-C#-D-E-F# over your A-D-E progression, two melody notes per chord. A, D, and E will be chord tones; the others won't.