 The series of numbers involved in these ratios (1 to 4, thus adding up to 10) was considered sacred by the Pythagoreans, who named it tetraktys. This metaphysical view of music as a reflection of cosmic order proved to be enormously influential in Western musical thought. As the harmony found in music is essentially the same principle as the one that regulates both the cosmos and the human soul, at least some Pythagoreans thought that their view could explain the effects of music on the listener’s mood and character.