As some may have seen, I do occasionally add in music tracks from Youtube into the chapters to add atmosphere and help instill the proper emotions with fitting scenes. Although I am curious.

Should I keep doing this, or does hardly anyone use them?

Hmmm, tis hard to say. Though music sometimes does add a new emotional level to a scene, it sometimes distracts the reader from the actual story, I've experienced it with other stories.

I'd say 60% of people would use them, but some people don't like music being added to the story and instantly stop reading and/or downvote it, again I've experienced it with one of the stories I wrote.

I did this instead, I added the music at the end of the chapter, a song that suits the mood. I'm adding 'Always Look on the Bright Side of Life' from Monty Python to end of the first chapter of my new story 'Jinx My Life', cutting off our protaganist mid-hyperventilation. It's so ironic for the actual mood, that it works well with it.

I think adding the music to end of the chapter would be a better bet. But continue what you want to do with the music, it's your story.

Certain music can settle a certain mood or atmosphere. Listening to soundtrack most of the time, I know that first hand.

So if you want to underline the atmosphere with music, go ahead.