Music is a part of culture, and culture is what people add to their social groups, tribes or race. 

Culture is a social thing, expressing stories, feelings, memories and values. For example, music is part of main culture as entertainment and communication. It's also part of classical culture (high-brow stuff like opera and orchestral works) and part of popular culture (contemporary stuff like bands and vocalists). World music expresses roots in tribes and native identities. Culture also includes sport and rituals. 
So, after the main things in life are in place: like order, safety, food and shelter, a society builds an expression of itself through these things. Music has the advantage over many aspects of the arts (painting, writing, sculpture and architecture) because you could say it directly communicates to people present even without them knowing much about it. It's immediate. 
One more thing about culture, it's made most of in peace time and music (like other cultural activities) can have a therapeutic effect on the mind and emotions. Hope this helps.