You have to go back in time and go to the Greeks where Pythagoras, famous mathematician and astronomer, is the first to discover the link between mathematics and the different musical tones. There were only 7 known planets at that time and that is why European music will only use these 7 notes. In Egypt, a musical note was attributed to each planet, but as there are 12 octaves, 12 astrological houses and 12 signs of the zodiac, the count was good. We speak then of "Music of the spheres", music that each planet would produce in the cosmos.