How would the remote xml file be changed by the end-user?

[Webmaster]

how would the remote xml file be changed by the end-user?
Each end-user has their own settings.

[Admin]

You can give each user an id number (that will be contained in toolbar) and store their settings in a database. Make a simple form to change their data in DB (add/remove songs). And make script that generates special include_xml file for each user according to data in DB.