How can music be sad?

During a dinner conversation with friends who had just returned from a trip to Lisbon I asked if they had heard any Fado singers while they were there. They said they’d planned to but one of their Portuguese friends told them the music was very sad so they decided to skip it. My reply was, “But if you don’t speak Portuguese, it’s not sad!” 

That was said partly as a joke because I own quite a bit of Fado music by Amalia Rodrigues, Christina Branco, Ana Moura and others and I agree with them, I don’t speak a word of Portuguese but some of those songs do indeed sound sad. 

But how is it that we are wired so that music stirs that feeling of sadness without words? Or happiness? And how universal is it?