You could save the steps of creating four individual custom fields by entering the following expression directly into the theatre view caption option:
if(isequal([media type],audio,1),[name] - [artist] /([album]/),if(isequal([media type],image,1),[events] /(formatdate([date,0],d-MMM-yyyy/))
[people],if(isequal([name],[album],1),[name] /([year]/) NP: if(isempty([number plays]),0,[number plays] LP: [last played]),
[album] - [name] /([year]/) NP: if(isempty([number plays]),0,[number plays] LP: [last played]))))
The end result is just the same, just a bit quicker to set up by entering the expression directly.
Also remember that it's quite acceptable to use expressions in the slideshow caption option too (see image playback settings). For example, mine goes like so:
if(isempty([caption]),if(isempty([events]),if(isempty([places]),[subject],[places]),[events]),[caption])
and ensures that if there's a caption, it's used,
if there's no caption, but there is an event, use event,
if there's no caption or event, but there is places, use places,
and if there's none of the previous, use subject.
All my images have at least a subject tag, so there'll always be something of some interest on show in the caption during playback.
-marko.