You need to reset / Set permissions to RWX for not just the Apple Loops Folder but all folders and files inside that folder..... to Everyone.... and clear ACLs and unlock..... again, for everything you are trying to share...
Do not do so for the entire drive unless it is an external data Hard Drive and not your system drive... Just the folder or folders you are trying to share.
You will likely find the excellent BatCHmod, the quickest and easiest way of achieving this...
http://www.lagentesoft.com/bm_instructions/index.html
The settings you will need to use, should look something like this after you have selected the folder you wish to share...
The owner name will be your User/Admin name... (It should be auto filled for you) leave Group set to whatever it is set to... and then check the boxes for all three categories and options as indicated in the screenshot.
Now click apply and wait about 5 mins before quitting Batchmod. even though it seems to complete the task quickly...
Note: make sure you have a full working backup you can restore your system drive from before attempting this as batchmod is a very 'dangerous' tool.. if used incorrectly...
Once done restart your Mac.. along with any other Macs that you are trying to share with and test....