With few exceptions, music has been for some centuries the art which has devoted itself not to the reproduction of natural phenomena, but rather to the expression of the artist's soul, in musical sound.

This quote means that, for the most part, music has not been about copying or imitating the things we see and hear in nature, like the chirping of birds or the sound of the wind. Instead, it has been an artist’s way of expressing their emotions and feelings through the sound of music.