A machine performs an ownership audit on source media files whose media tracks are used, or proposed for use, in a mash-up media file. The machine may access a first group of media identifiers from a user's media library and identify authorized media files that the user is authorized to play or use in a mash-up. The machine may access a second group of media identifiers that identify source media files selected by the user for inclusion in a mash-up. The machine may determine whether all source media files are authorized and then present a notification that indicates whether the mash-up media file can be generated, or has been generated, exclusively from authorized media files. If a source media file is not authorized, the notification may include a suggestion that the user purchase an authorization to play the media file, use it in a mash-up, or both.