This question might seem easy to answer at first. For example one could say that music makes us feel good, that it helps us relaxing. These explanations refer more to the nice effects of music, but cannot be the origin for our capability to make and understand music.
Actually, people around the world are trying to find answers for the fact that music is omnipresent and why it is essential for us as human beings. Did it, for example, play an important role in the evolution of our species? A “music gene” is discussed, which could have been developed hundreds of thousands of years ago, giving an evolutional advantage to those who possessed it. Music is a group building subject, so maybe humans with a sense for music could build up societies more easily compared to non-musicians.
In my opinion it is clear that music must be something basic – like an instinct – for us. It is ubiquitous from indigenous people in South America to our modern western civilization. One does not need to study it like a foreign language. Even if it is a kind of music you are not used to, you can still understand its meaning, i.e. relaxing chimes or stimulating beats. The oldest discovered instrument – a bone flute – is about 40,000 years old and scientists suspect that vocal music dates back at least twice that far.
But my opinion is not shared by all scientists. Some say that music is useless and that it is more or less something that could vanish from our culture and leave the rest of our lifestyle virtually unchanged. They see no evidence that music might have granted an evolutional advantage, i.e. more offspring, to those humans with a sense for rhythms or melodies.
The question remains to be answered, but anyway, would you like to live without music?
http://www.healingmusic.org/Library/Newsroom/WhyDoWeNeedMusic.asp (last access on 01.07.2012).
Mithen, S.; Singing Neanderthals: The Origins of Music, Language, Mind and Body; Phoenix House; New Ed (2006).