That's because TTrack entity doesn't have a field mapping back to TAlbum. So all association information is in TAlbum, and that's the only "side" that can be used to setup a relationship between albuns and tracks.
To do what you want, you need first to map a bidirectional association, by adding a FAlbum: TAlbum field in the TTrack entity. Then you should modify the ManyValuedAssociation attribute in album entity to refer to FAlbum.
That process is also explained here: How to Access Parent Entity - #2 by wlandgraf
Note that, when you do that, you must always explicitly set the TTrack.Album property, it will not be set automatically even if you add the track object to the TAlbum.Tracks list.