I don't think you can do this under Playing Now (not talking about display view as you get the player in the screen if you want)
This would be great to use the optional text capabilities of the player bar under standard view. Where I would really like this is in JRemote ... if I remember when asking the dev Robert to change the playing now text he said it would have to work for theater view to port it over to JRemote (might have misunderstood, but that's the gist of it).
I can live with this more or less in theater view generally because of the file info panel .. but especially for classical music this would be great to have two configurable playback options -- that way you could indicate whatever fields (probably some space limitations to respect though - but Artist and album seems doable (or Work/Composer for classical as an alternate). If two lines like the player window has space wouldn't be an issue really.
If I have missed how to after all this time.. please someone chime in, otherwise I'd like to suggest that playback text be configurable like in standard view
(or better it is part of options by zone ... but hey whatever can't wish for everything right? :p )