The movie one I linked to is pretty complicated. All you need to do is create a couple of new fields under Tools - Options - Library & Folders - Manage Library Fields
1) Create a new field called Tooltip and under Calculated Field put [Tooltip - Audio]
2) Create a new field called Tooltip - Audio
3) For the calculated field for Tooltip - Audio just list the fields you want displayed. If you look at the current Audio tooltip you will see it is just a bunch of standard fields. Just add [Composer] to the group of fields you want and you should be all set.
Example for the calculated field.
[Composer] [Album] [Name] [Date]
[Sample Rate] [Bit Depth] [Channels]
If you want a different tip for classical and non-classical just use an IF statement to, for example, use [Composer] for classical and [Artist] for non-classical. Once you have that working, go crazy and add sorts of bells and whistles, like the Movie one has.