I have long been trying to find out what that tingle on in my mind is whenever I hear a musical passage I love. Without a doubt, everyone who listens to music, whether a musician or music lover has this experience. They are either unaware it's happening, or they know it's occurring but can't define it. The latter happens to me, specifically, in instrumental music. 
Here's an example: 










Brahms' Symphony No. 4 in E minor. The beautiful first movement is my favorite and I listen to it in its entirety frequently, but there is a passage (5:14 - 5:30 in the video) that the moment I hear it, I feel a pull or a tug in my brain and I have to play that passage over and over again. It's as if those chord progressions and arrangement of notes reach the pleasure center in my brain and poke it, making it itch and making me want to scratch that itch by listening to that passage over and over again until I am satisfied. In other words, I have what is popularly called, an "eargasm." But I would almost call it a "braingasm" because while the sound is coming in through my ear, it is in my brain where I feel the sensation. From there it radiates throughout my body like energy. Sometimes it makes me cry from the beauty, other times in other pieces of music, fills me with passion and love. 


Classical music is where I notice this happens the most (to me personally), but there are also passages in some rock songs and in other genres where I have this experience. 

Everyone has had this experience, I'm sure. But why/how does it happen? Reasons I can think of correlate to music theory and the very way that musical pieces are composed: the key of the piece, it's chord progressions and so forth. But everyone responds differently to different sounds, so I'm not sure if that's the cause. That passage I highlighted in the Brahms may be the pinnacle of musical bliss to me, but for someone else it may not be that all significant. Does it have to do with my own personality and my tendency to like certain sounds? Or is there a technical aspect at work that causes something like that to happen in my mind, or in anyone else's? 

It is so difficult to explain something to subjective, but I hope someone understands.