Unite the world, yes.

Save the world, not likely.

IMO.

I do not hear the music will save the world.

But popular russian novelist  Dostoevsky said : The beauty will save the world.

Your teacher is right too. Because, the music is a strong thing.Who loves music really never can fight,they can like,they can love,they can be happy,they can be sad,they can feel all kind,nice feelings.So the world will be saved:)))

I don't think so.

that's good idea. thank Tris

when you hear a sad song. how do you feel? 

when you go to club, you will be agitated by the songs in club.

for example. they let the solders hear national song to encourage their spirit to fight. that songs make them active, brave