"The operation can’t be completed because you don’t have the necessary permission."

I'm not currently able to drag MP3 files into Music like I always used to be able to. I searched the forums for answers to that question and was told to make sure my permissions were set to Read & Write.

As above, they are currently Read only for 'wheel' and 'everyone'.

When I click the arrows to change to Read & Write, I get the message "The operation can’t be completed because you don’t have the necessary permission." I am the only user/account on this computer and always have been. When I go to System Preferences my account is an Admin account.

How can I fix this so I can change the Music permissions??