Mythology and folklore speak of music as a magical force.
Sounds associated with enchantment and sorcery are at a far distance from contemporary understanding, being associated with narratives of extraordinary events. But there is more.
When music is central to tales of the strange and paranormal, attempts to evoke its nature falter. It is invariably described as otherworldly, beautiful, mystical... and altogether unlike anything that would fit a modern definition of "music". It defies memory of rhythm and melody, leaving only a deep, lasting impression of high strangeness.
The composer would do well who would evoke, and repeatedly express, this formlessness.