As a musician, maybe the thing I want to do is release my album as a XSPF file that associates each specific mp3 URLs with an identifier that is also my URL, e.g., the page I’ll create for each song, or the fragment for that song on the album’s tracklist page, etc.

Although acting as a database of “authority” records is not particularly within the scope of XSPFs use cases, there’s some sense in this in that one of the biggest issues is getting music players to use more concept-oriented identifiers than just file locations–there might be a natural step for players who support XSPF in general to evolve to more interesting uses of XSPF identifiers.