If you are like me, you download preview or sample music to work off of to provide a rough. You can't commit to the cost of the file until your client is sure. But how do you keep track of where you found the file? CMD - I in Mac. Command I opens the info section of a file that is highlighted and near the bottom there is a section where you can add text information, this is where you can copy the location of the file as a reminder later on. Simply copy the URL of the files web location and paste that into the comments.
Bonus tip, use CMD - L to select the address in your web browser then follow your normal copy/paste shortcuts.