Lived in the seventh century AD, Isidore was the Christian theologian who more than others gave absolute importance to music. He came to affirm that without it there would be nothing. 
Also Boethius recognized in music the function of approaching spiritual reality, which went beyond the simple physical, mathematical and mechanical nature of composing or playing. However, Isidore claims, in his Etymologiarum sive originum libri XX, that without music no discipline can be perfect. 
According to Isidorus, music is the fundamental knowledge, the one the universe can not even exist without. Music reproduces the entire structure of the universe, which moves armonically.
On the other hand, music has important effects on human behaviours in different circumstances. Isidorus reveals the power of music over the human soul as well.

This is the text we chose from De musica:

Isidore de Seville - The power of music pdf