The Relevance of Scale in Music

The same notes can be performing different functions. They field different depending on key, depending on the scale we are tapping into with those notes. In c major, the g is the perfect fifth, and c is number one. Once scaled down in a minor, a is number one, and the g is what interval from a rocket out? So that's e relevance of scale or key in music. We want to have seven letters for the seven different notes of a scale. Using a to g plus sharps and flats insures that every time we go up a degree in any scale, major or minor, we go up one letter - never two.