Originally Posted by butterblum
Doesn't this hide the actual mp3 files from apps such as Google Play Music?
Yes, it does hide all mp3 files also; not a solution.
As far as I know, there is no solution. I just use Quickpic and remove the in-built gallery/album app (or just don't use it, if you don't want to remove it). With Quickpic you can pick which folders you want to include, or pick which folders you want to exclude, or hide. A lot more versatile than the default Android app, and 10 times faster.