First I will speak a little bit about music without text. And then about what happens when you combine music and text.
Sigmund Freud was afraid of music (1).
He was not afraid of other artistic forms. He could stand in front of a painting and observe it for a long time. He could reflect upon what he saw. But with music it was different. Since music is abstract, he could not understand what it meant and how the music could have such an emotional impact on him.
Do we know more today?
Yes. We know now a lot about the physiology of the brain. The brain is made of cells called neurons. These communicate with each other through an electro-chemical system. A neuron fire an electric signal that triggers the release of a chemical neurotransmitter, for example serotonin and dopamin.