Imagine you are a painter wishing to capture beauty with your brush strokes. You might begin by placing a clean canvas onto your easel and preparing samples of the colors you wish to use.
What if that canvas is dirty?
What if you spill some blue into your white paint?
Your inspiration may be powerful but, if your basic materials are flawed, your final creation won't reflect your vision.
Think about this lick from the Mozart Requiem...
Can we make an argument that, before we get into the nuances of this (or similar) passage we have to demonstrate the basic control over the instrument to simply be able to play it very clean and accurate, not favoring any particular note?
Turning the notes of an excerpt into a kind of exercise
might be called "canvas work."
In other words, building the technical ability to play these notes very accurately and evenly is similar to preparing a canvas and your paints so that you can then begin to create. It takes discipline to realize your inspiration.
Or maybe I'm wrong....
Maybe the nuance and subtlety have to be there from the very beginning.
Consider these two examples:
You start by making it very solid, technically and then add in musical expression.
You start by making it very expressive, musically and then clean up the technical details.
Or maybe even that isn't correct because it assumes a binary simplicity. Anyway, this is a subject I've thought about before (in blog form).
Here's a 2010 post, along similar lines.
Here's a 2011 post, also similar.