how to add new items to certain file extension context menu

how to add new items to certain file extension context menu (to .mp3 files for instance)

I've also noticed that there is common items in all context menus across the windows, does they all share/inherit one context menu ? where is it : which one is for text

what such keys are called and how to generate them (for instance {11dbb47c-a525-400b-9e80-a54615a090c0})

also is there a good brief reference for the registry that you would recommend ?