Now I know that I'm more retentive than most. But here goes!
All music, classical, pop, even heavy metal, has a composer, somewhere along the line.
Take, for example, Queen. A lot of their music was composed by Freddie Mercury, and some by Brian May. Some were collaborated efforts from the whole band. While I realise the unliklihood of wanting to listen to some "Brian May", the fact remains that he did compose it.
Similarly, I find it amazing that Johann Sebastian could possibly play the instruments in an orchestra (all at once) and possibly also conduct. As such, I use a artist field that consists of "[ORCHESTRA] [/ CHOIR] [/ SOLOIST(s)] [/ CONDUCTOR]" to end up with a field:
> Boston Pops / Fielding
or
> London Philharmonic / Tikanawa / Smith
This is for searching purposes only since I have other fields which are used to group soloists, conductors, orchestras and choirs.
Perhaps this bloats my tags (well, actually it does!), but I appreciate the "completeness" of the information. At least, if someone says to me: I really like David Hill's organ playing -- I can see if I have any David Hill and play it. Or that they enjoy Arthur Fielder's conducting... etc.
It's not a requirement, by any stretch of the imagination, but just makes me feel all warm and fuzzy inside... Or something.
Anway, that's my opinion on the subject of how to tag them.
I also keep Pop and Classical together in the same DB. I sort them out by means of a few smartlists.
I keep a genre field for all classical music that groups it in to categories such as "Sonata", "Symphony", "Suite", or even "Classical" for those that I can't be bothered to classify. My smarlist then has the rule:
> Genre=Sonata,Symphony,Suite,Classical,Concerto, etc...
I have created a Media Library Group in addition to Audio, Video, Images of "Classical". This simply has the rule "Playlist=Classical" associated with it to only use the music in the Classical playlist. In the "Audio" section, I edited that to show "-Playlist=Classical". This forces it to ignore everything that is in the Classical playlist.
An aside: I use the Year field for the year that the piece was recorded and have a separate field for Year Composed. This allows me to have smartlists that can automatically group music from the Baroque, Classical or Romantic periods very easily. Of course, this is a little more grey than black and white, but it seems to work really well.
I hope that this gives some of you some ideas for your own DB's!
P.