iTunes music folder: 15GB of disk space unaccounted for?

[mgpg89]

Below are two screenshots:
1 - my iTunes library with ca. 82GB of music
https://dl.dropboxusercontent.com/u/2264334/Schermafbeelding%202015-05-11%20om%2009.15.05.png
2 - the size of my iTunes music folder, which is about 97GB in size
https://dl.dropboxusercontent.com/u/2264334/Schermafbeelding%202015-05-11%20om%2009.15.43.png

Now I'm wondering ... where is the other 15GB?

Side notes that may or may not be relevant:
* I have no movies, podcasts, TV shows or apps in my iTunes library ... just music
* I have 128kbps AAC converting enabled for the music on my iPhone and iPad: maybe these files are stored locally? But if so, I can't seem to locate the files?

Thanks for your help.

 

[Kissmyne]

There isn't really enough information to give you any for sure answer, but I would look at the contents of your iTunes Media folder and look at the sizes of the files in there, odds are, after looking at the folders inside iTunes Media, you will have your answer.

 

[mgpg89]

There isn't really enough information to give you any for sure answer, but I would look at the contents of your iTunes Media folder and look at the sizes of the files in there, odds are, after looking at the folders inside iTunes Media, you will have your answer.

Thank you.
I had DaisyDisk scan the contents of my iTunes Media folder and discovered that there's around 15GB worth of music that I deleted over the years, but apparently I didn't click "move to trash can" ... I just deleted them from the library.

So now the question is: is there any way to delete music from the iTunes folder that isn't in my library?

EDIT: seem to have found a solution myself
I re-added my entire music folder to my library, but luckily iTunes is smart enough not to add any duplicates. So just the newer stuff (I don't want) gets added at the top of my Recently added smart playlist, which allows me to easily delete said files.

 

[mgpg89]

The solution posted above was only partial, so it seems ...
There's still about 6GB I can't seem to locate.
Anyone got any suggestions?