Whyt do the hairs on the back on my neck go all prickly when I hear a good tune

I am an MD. That is an extremely good question, but it is unfortunate that we will probably never know the answer to it. However, I will take a stab at it. I have a Labrador Retriever dog, and whenever she gets REALLY excited about something, the hair on her back stands up. It is usually when she is scared or angry, but can also occur when she is happy to see me after a long absence, etc. I believe this reaction is tied into the adrenalin "fight or flight" mechanism which is a very primitive survival program that is hard wired into our central nervous system. It must have enhanced survival in some manner, perhaps by alerting our adversaries that we mean business, or maybe just to make us look bigger and more formidable as an opponent. As to why humans get such powerful emotional responses from music? That is an even harder question. But positron emission tomography studies show that music evokes and amplifies our most primitive emotions, especially in the Amygdala of our brain, which is deep within the brain and very separate from the cortex. In short, it is a primeval response of uncertain etiology, but fun to speculate about!!