How Do Music composers decide which notes to use to convey emotion?

There is no formula to follow to create emotional melodies. Actually it has more to do with how it is played than how it is written, although how it is written is a factor.

This is to get you started: Happy - C major to F major -> play the C-scale to this Angry - E minor to F major -> try to find the scale for this. I don't know it off the top of my head. Sad - A minor to F major -> play the C-scale to this.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.