Thank you, that is a reeeealy good idea.  Why haven`t i thought of this before... 
Well,  to be serious again.  I think,  it's an essential feature of a DJ software,  to be able to choose what is listed in my library and what's not.  
I use "player pro"  for playing audio,  wich also uses the android media database.  In this app,  i can easily choose a   specific music folder.  All other folders containing audio are hidden. 
Anyway,  I found a workaround for my problem:
I moved all my folders containing audio that i don't want to use in cross-dj into one folder and renamed it,  starting with a dot.  When i do a media rescan (widget),  android will not scan this folder. 
Unfortunately,  if i want to play music to my daughter,  i have to rename that folder again,  remove the dot and do another media rescan. 
Perhaps its possible to write a batch script that does all those steps in one click,  but i'm not a programmer. 
But hey... Actually,  that should be your job 
