So I'm looking for a term or name for this concept. Its that..."thing" in music that don't seem to accompany or service the melody nor is it rhythmic. Maybe its a simple as calling it a sound effect but thats not getting me the sources I need.

My first example is the screeching string in the first few seconds of this video. That sound that you associate with spiders:

https://m.youtube.com/watch?v=bMgvR58ODfc

As my second example. At the phase shift of this boss's soundtrack there's this ambient bit at the 2:41 mark. Its also present in the games sound track as textures, dissonance or undertones of sound/tone:

https://m.youtube.com/watch?v=oNN9GrkIPio

Its that part where the narrative and music seem to meet. And I guess that why I'm interested. I'm not well versed in music theory but I've learned to write through trio and error. So I hope you'll forgive me if this is a stupid question.