They are all correct, StevenG. You bring your own interpretation and feelings to a song. You may do a song at a different tempo or volume, you might evn change the tune or the words, or even write a new verse. Some purists my grouse about what you are doing but make sure you listen to the whole range of comments. Don't let negativity change you but be aware of the changes in your audience. If you are doing something that means a lot to you and you aren't drawing any audience then there is something wrong with either your presentation or with what you are doing.