I work on another music file management system, my personal special hell is playlist files. An m3u playlist file is just a new-line separated list of file paths, which can be relative or absolute, and potentially encoded in whatever locale is set on the users computer. Some fun issues:

* Windows and Mac filesystems are generally case-insensitive, so some users will have the file names in the playlist file in one case and the actual file names on disk in another format * Sometimes file paths cross between two different filesystems, because one is mounted in the other with a USB drive or over CIFS or similar. Sometimes these two different filesystems have different case sensitivities * There's no way to know how the playlist file was encoded * HFS+ normalizes file paths to Unicode NFD, but there's no guarantee that the paths in a playlist file will be normalized. Also, sometimes users generate an m3u file on a Windows system and expect it to just work on a Mac. Also, the filesystem nesting problem with network or USB mounts can happen this way too.