To elaborate on the Cymatics post - certain frequencies are more in harmony with nature (think literally "harmonized" like a chord). As our entire existence is based on frequencies (you could say we ARE sound), sound effects us a lot. And of course there's a massive polarity spectrum - I'm sure everyone can recall a time that a loud/piercing sound made them feel uneasy or on edge, and another time where they felt soothed by sound (for example, the flow of a river or sounds of nature).
Sound Healing also exists as a spectrum (in my opinion). The majority could be generalized as the intentional use of certain sounds or frequencies to help us feel relaxed, aligned, peaceful, and more... this could go deep but we'll start with the basics. There is much diversity with acoustic instruments (all kinds, styles, tunings, etc.) and ambient electronic productions (likely recognizable as meditation music).
On the other side of the spectrum, Metal music can be extremely therapeutic, as it allows us to confront, feel, and purge negative emotions. Of course, everything is best in moderation, but anyone who enjoys heavy music probably gets what I mean.
In this forum, I have posted some of my favourite frequency tracks. Generally I find they relax me and reduce stress. I like to throw them on when I'm working, relaxing, hanging with friends, or meditating. It's fun to explore how different tracks resonate with you (in your body, mind, and emotions).
For those who may not understand the concept of Metal as therapeutic... I can't speak for everyone, but this is my personal experience. It's a catharsis to embrace and purge negative emotions. I can feel heavy with hurt, anger, or sadness, then listen to my favourite bands, and walk away feeling cleansed. I believe this powerful emotional outlet is why metalheads are generally known to be nice people. By accepting, confronting, embracing, and releasing our darker energy we create space to be lighter. Everyone needs some kind of outlet... more on this in the "Shadow Work" section.
Sound heals us across the spectrum in different ways. Tune into what serves you best!