This is an embarrassingly basic question, but it's been in the back of my mind for a while, and I haven't been able to find an answer.
I've been studying very basic music theory lately and trying to write some simple songs. My process is to do these three things in order:
- Write the percussion
- Come up with a chord progression and lay that out
- With another instrument, write a melody on top of it all
My question deals specifically with part 3. As I understand it, a "scale" just means a palette of notes from which to choose when writing out the melody (please correct me if that's an oversimplification).
My question is this: does the scale change each time a chord changes in the chord progression (i.e., should I be choosing from different notes each time the chord changes)? Or should I be sticking with one scale that's determined by the overall key of the song?
I had assumed the former, and for example would be writing the melody in D major for the part where a D major chord was playing, and then using a different scale when the chord changed, but I'm starting to think my assumption was built on a misunderstanding.