What makes sad music sad?

the vibes of the music

A slower tempo played with softer instruments like a violin or the piano will do it. Even acoustic versions of songs are a little more sad than the original versions. But I see sad in everything if I look or listen close enough.

I can answer the first part of your question. Many 'sad' pieces of music are played in a minor key, which makes the sound more melancholic. If you know someone who plays the piano really well and who can muck about with the tune, ask them to play something familiar, then ask them to play it again in a minor key (as much as they can, its not possible with everything whilst keeping the tune). You'll be amazed at the difference.

A lot of times, a "sad" song will be a slower song in a minor key. Minor keys natural give a feeling like that.

i think its the melody. it also helps if you research on the person who made the music. if the music sounds sad then most likely the person who made the music will have some sort of mental illness. i also think it depends on how you are feeling and imagination. anyways thats just my opinion.

i have no idea but i guess if the music is really slow or something like that you asume its kinda sad but if the music is fast pace and you can bang your head to it it seems like its a happy song.

sad songs have a slow tempo and music in a Minor key.

I would say the mood you're in at the time combined with a minor key.

I think the melody

it can probably be both, the melody and the harmony. i dont have a clue, though