add a reasonably big textarea in the submission / edition form
add a right aligned column in the track list, with "context" / "remarks" / "intro" (or a suitable icon) as link text. Clicking on this displays the context written by the submitter underneath the track row in the track list (via javascript).
I think it would be cool to add an intro / context field so that the context of why the song was chosen could be archived if the submitter desires so!