After reading FT Shark's-Encore-Authoring-Guide I have the following idea:

Is it possible to create a menu with Encore/Photoshop that points to trackname.mp3 saved outside the VIDEO_TS-Folder (possibly in AUDIO_TS or in Folders like Interpret\Album\)?

Or could I try to use IFOEDIT to point to such a trackname.mp3?

(My player supports playing mp3, but don't show the long file names on TV-Screen - any other workaround for that?)