It’s quite simple - actually I don’t know exactly. But in my experience, to write a good melody you must always bear in mind that a melody is a kind of horizontal conversation of sounds, one after the other without repetition. Each sound should sound new, should sound different so there must be no repetition within this melody. Or maybe if there is repetition, this repetition must have a different note value, so even if a note is repeated in term of metric, it should have a different value for the ear of the listener. So the melody must create something new in each single sound. There must be no repetition. That’s the real, the only way you can come up with a melody – or this is my experience.
When you write a melody, you must pay a lot of attention to the intervals between the notes – each interval must be different from the previous one just to keep this idea of novelty within a melody.
But there is not a rule, when you go to the Conservatory, they don’t teach you how to write melody. This is a rule that I developed based on my experience. Some people say it’s all about inspiration, but this is not true. I have only discovered this later on in my career.
The possibilities are enormous – you can really reduce the minimum the intervals between the notes, or maybe you can take them away, and you have a melody like a kind of horizontal line with wave-like movements. The music for Cinema Paradiso is an example of this. (Ti, re mi ti la sol la do fa mi mi re.) The movements of a horizontal line.
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Everything starts with an idea, it’s the first thing I look for. You can’t write anything on paper if you don’t have an idea, whether you’re talking about music or poetry. The first thing is to go through this process, which sometimes is very demanding and very exhausting for me, because you cannot stop at the very first idea you’ve got. You have to go through and analyse all the different ideas and then try and find an idea that can be flexible (ductile) and can be adapted to the film. When I say idea, I mean the smallest or the tiniest thing (minima) that in my opinion could become something else, could be developed up to the point of becoming a musical composition.
Source:
https://www.classicfm.com/composers/morricone/how-to-write-film-score-hateful-eight-tarantino/
