My car stereo system allows for playing mp3 files off of a USB stick. When mp3s are in subfolders, it makes it difficult to jump songs predictably. Easiest way around it is to flatten all mp3s under a single folder.
I found this post describing how to use powershell to do it. Here is what I'm using for my own reference:
(ls -r -include *.mp3) | % { mv -literal $_ $_.Name}
