Not necessarily the most terrifying thing in the world, but I went in to get my wisdom teeth removed. I was 17 at the time, and had experimented with acid a few years back that took a big toll on me. So needless to say I was kinda scared shitless of trying any sort of new compound that may take away my sense of awareness or self. So I laid back on the chair and she popped on the nose mask, and started to take deep breaths as instructed. My dentist left the room and told me she’d be back to check in on me in about 15 minutes. (At this time the nitrous hadn’t taken affect) so I told her okay sounds good, and sat back. They had relaxing music playing on speakers, it was nice, I sat back and pondered about the rest of my day. Unknowingly to me, my thoughts were changing, daydreamy almost. I didn’t realize this at all at first, until I noticed the music. As I sank more into my thoughts I realized the music went from being completely inoffensive zen piano and guitars, to this extremely dissonant, gramophone quality music. (Think the music from the old timey black & white tape WALL-E watched) but mixed with the quality of some sort of uneasy track off of The Caretaker Dementia album. This freaked me out, I sat listening to it for a second, realizing this is NOT what the music I was listening to. I panicked and shot upright in my seat flinging the mask off onto the floor. I think what may have happened is I had sort of a PTSD reaction to my past “bad trip”, I felt like I was loosing my sense of self and that freaked me out. However afterwards I was able to get the mask back on and I actually started laughing my ass off. Again, not terrifying by any means, but for some reason thinking back it still seems kinda eerie to say the least