Become a fan of h2g2
As you travel around the world or even just go down the road to the shops, you'll probably come across music of some form or another. You've undoubtedly noticed this yourself, and thought 'My, what lovely music,' or 'What the hell is that noise?' or even 'Good Lord I hate Muzak, Tommy Tedesco has a lot to answer for.' Whatever your personal taste in music it is fair to say that almost everybody listens to, and appreciates some form of it.
So what's it for?
Good question that. Some would argue that music soothes the savage beast, though exactly which savage beast that would be is left up for grabs. It's highly unlikely that a charging Bengal tiger, with you in its sights and it's blood up, is suddenly going to change its mind about you not being lunch simply because you start playing Barry Manilow at it1.
Others would have us believe that music is a form of artistic expression, and much like a beautiful painting can give us an insight into the artist's soul (regardless of the fact that some of these so-called artists seem to have souls that look suspiciously like the gloomy, smoke-filled interior of a 16 year old's bedroom after a heavy night of angst-filled rhetoric and joints the size of cigars).
Alternatively, music could be considered to be the avenue down which lovers stroll (arm in arm, gazing into each others eyes and whispering sweet nothings to one another). A catalyst to a romantic liaison, the likes of which neither has experienced before, brought about with the aid of the musician's equally romantic mind.
Music is an entirely subjective thing, meaning different things to different people; bringing forth emotions and memories that change depending upon who is listening to it. You may have heard a piece of music somewhere once, when something important has happened to you, and then every time you hear that piece of music again you're reminded of that incident (causing you to cry, smile, laugh, or find a wall to put your fist through). Just as no two people are the same, no two people's response to a piece of music will be the same. Similar responses may be produced; more than one person may feel sad listening to the same song, but in all likelihood they will be thinking of different things that the said sad song2 puts into their minds.
An important part of human existence, since it tends to be almost everywhere we go, music has been with us since the dawn of humanity. Ever since cavemen learned to bang rocks against one another to produce a loud cracking noise, musical sound has been part of our cultures; from the percussive rhythms of African tribes to the wailing, big-hair antics of the European glam-rock guitarist. One way or another everybody gets into music somehow.
As to why it's part of us - who can say? Possibly it is an insight into the more sensitive side of human nature, possibly it's just another attempt to get into somebody's underpants.
Hell, maybe it's just bashing rocks together.