Amarok seems to know about the Composer field in a track description, but it doesn't include it in the summary or display it when the track is playing. Is there any way to tweak Amarok so that the composer will be displayed? This is of particular interest when listening to classical music.

You can configure the playlist layout to show it: playlists -> playlist layouts -> configure playlist layouts

anywhere else and you'll need to post a request (as best as I can tell)