Theorys on the relationship between music and the mind?

[KomodoMK]

Music to my little fishy is very powerful, so much so that he would rate it his #1 drug. I would like to understand the mechanics of how it affects the mind and central nervous system, and how it can produce such powerful effects. Here are some of the things that puzzle me that I hope someone can give insight on or at least provoke a good discussion.

Little fishy loves MDMA on it's own, it produces feelings that words can't describe, but the potency of this chemical seems to increase 10 fold if he plays his desired music. The effect of this is of such magnitude that MDMA without music almost seems dull. The music tends to mainly increase the euphoria. Where people generally say drugs increase music appreciation, little fishy would say the music increases drug appreciation. Does anyone know of any scientific reason behind this phenomenon?

Another thing that puzzles me is why is music so prominent when it comes to association with memory's and emotions? Why can music have such a huge impact on your emotions and influence your mood to the extent in can make you over the moon with joy or cry your eyes out?

Has anyone ever experience a 'shudder' feeling that reverberates down your spine or had the head tingles (feels like all your hairs standing on end) when you hear a song that means a lot to you due to association with a memory, emotion or both? What triggers that?

How come our perception of what sounds good and causes these effects on the mind differ so widely?

There are so many questions but these are good to start with. I think there has to be a lot more at work here than simple changes of neurotransmitter levels in the brain. Maybe it a complex effect on many of the neurotransmitters?