When I changed from my iPhone to my Samsung S8, Samsung was nice enough to provide a little program that copied all doc and media files (including all my music) to my S8. Went flawlessly. Now all my music is in the iphone/music folder. Photo's are in the iphone/Pictures folder.

But I see there is also a DCIM folder and a Music folder in the root. I can see the DCIM folder holds all the photos take with the Samsung S8. The Music folder currently holds no files since I didn't copy any to it yet.

But I was wondering: when apps use photos, videos or music, they find ALL photos, videos or music, even though the files are scattered in different folders. Where in the system is it determined which file goes where, where the system needs to look for certain files and can you alter that? (probably yes, it's Linux, but where?)
Also, this probably means I can freely copy files between these folders?
I'm asking because I would like to add a 128GB microSD card to the S8, and then copy all music to there. Can I simply and safely cut and paste the music from the iphone folder to the SDcard?

Thx!