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?

there is a main 4 note sequence and the cadence and up-down cascade of the four notes is what carries the flavours or emotional depth of most music.

Rick Beato has a great video on this. Can’t remember the proper name of it. But once you watch the video, you’ll never think of music the same way again.

It is tied to how we express emotion in language, one might say.
To see what I mean, follow the note ’up-down’ sequencing in this, a little bit called ’Amber’.

A near perfect example of injection of emotion in music. Think of being told a story.

A melancholy message and how the voice would carry the meaning, the intensity and depth, the power of the words.
Music to hear, why hear'st thou music sadly?
Sweets with sweets war not, joy delights in joy.
Why lov'st thou that which thou receiv'st not gladly ...
I'm not sure humans understand why some music or songs bring a tear to your eye.  A nice cut of Amazing Grace, or The Mystic by Morrison, or Islands in the Stream, by Dolly P. & Kenny.  The list goes on, it's amazing and wonderful!!
Islands in the Stream and Amazing Grace? Wow, that's surprising. The one is a pleasant pop song to me, and the other is an overexposed bore.
"once i was" has hardly any minor chords, just one i can tell, but it definitely is a heartbreaking song. a variable combo of minor/diminished chords and sad lyrics plus a lilt/catch/quaver in the singer’s voice, seems to be the valve that turns the waterworks on.