I don’t like to contradict those with more experience, but my advice would be NOT to automatically add music to iTunes library. As far as I’m aware it doesn’t confer any advantage. It doubles the amount of storage space you need to use, if you keep copies outside of the iTunes library, and if the file becomes corrupted you have to navigate the files yourself. This is not always easy as I’ve found iTunes sometimes organises files in a way that doesn’t fit with how I think about my collection. I find I organise my music better which is helpful when using a programme other than iTunes.
What should be done is back up, and consider doing so twice. You can do this without iTunes organising your files. I use both a local external drive and an online storage service. Perhaps I’m paranoid, but if someone broke into my house and stole all my computers etc I wouldn’t lose all my music.
