The breath is so important. When we're stressed, we breathe very quickly, shallowly, from the top of our lungs. When we're more relaxed, the breath drops into our belly. We're still probably breathing from the top of our lungs because this is how we've become conditioned.
By deliberately focusing on belly breathing, you bring the breath down lower and are telling your body that you're safe and you can slow down.
I was watching “Backrooms” yesterday, and the way the movie brings you in is through the breath of the point of view of the character that we're focusing on. When they're panicking, they're breathing very shallowly. You can hear loud, quick breaths. It's much more effective than music. I noticed this because I wanted to watch it from a distance and not get drawn into the fear, to just understand the concepts, and it worked very well.