iTunes: Changing Apple ID Username/Email

I can't seem to find consistent answers of this question I have on Google, but does anybody here know what exactly happens if I want to change the email address/Apple ID associated to my iTunes account? I'm currently using a HOTMAIL email address, but I want to switch to an @outlook one I just made just by going to the appleid website and changing the ID and email address.

But if I do so, what happens to my previous app and song purchases? Will they still be tied to my hotmail email ID? That is, if I were to re-download them after changing to an outlook email ID, will it try to authenticate me using the old apple id or the new one?

Thanks in advance great people of the Interwebs