I've been at this tagging issue since 2006 when I first bought an iPod video for experimenting with classical music on the go.
I never much took to listening to classical via in-ear phones, but with the purchase of a car with a rudimentary ipod interface in 2007, I ripped my entire classical collection for use in the car, and now use Media Centre as my music "server" for home listening.
Some of the unique aspects of classical that I found needed to be addressed were:
1. in a large classical collection, it's likely that there will be multiple versions of the same work by different conductors/orchestras/artists
2. it's possible that there will be multiple versions of the same work by the same artist/conductor
3. each album for each artist needs to be treated as a separate "work", otherwise simply labeling all Beethoven's 3rd Symphonies as such will end up with multiple artists' versions all being merged together under one work
4. it's preferable for most cd's or downloads that contain different works (Beethoven 5th and 7th symphonies) to be separated into separate "albums" so that each can be located separately when desired.
5. the use of a single genre "Classical" doesn't cut it, - classical needs to be tagged with sub-genres set up that enable separation of the works into logical groupings (doesn't matter what they are, as long as they work for the user doing the tagging).
Here's what I've developed over time that works very well for me...
Genre:
I've ended up evolving to a number of different sub-genres as follows:
Classical - Orchestral (everything with an orchestra that isn't a concerto, choral or music drama)
Classical - Concerto
Classical - Piano (solo piano)
Classical - Violin (solo violin)
Classical - Cello (solo cello)
Classical - Chamber (everything that's chamber except for solo piano, solo violin and solo cello)
Classical - Vocal
Classical - Choral
Classical - Music Drama (my Wagner is showing)
Album Name:
Each cd is ripped, or download processed, so that each major work is then separately labelled with the appropriate composer, work name, and artist in the album name to allow the work to be generally identified from the "album name" value, for instance:
Album: "Bach: Sonata #2 in A minor BWV 1003 (Ibragimova)"
....or
Album: "Mozart: Symphony #35 in D, K.385 "Haffner" (Mackerras SCO)" and Album: "Mozart: Symphony #35 in D, K.385 "Haffner" (Mackerras PCO)"
....to distinguish two separate recordings of the same composer's work by the same conductor.
Album: "Bach: Sonata #2 in A minor BWV 1003 (Ibragimova)" (for a work where there are multiple different albums by the same conductor)
Artist:
I tag artists by last name so that they're alphabetical:
Artist: "Abbado: Wiener Philharmoniker" (for an orchestral work),
Artist: "Fischer (Julia), Sitkovetsky: Academy of St. Martin in the Fields" (for a concerto, to identify both soloist and conductor),
Artist: "Ibragimova, Alina" (for a solo artist), or
Artist: "Ashkenazy, Perlman & Harrell" (for an un-named trio of artists)
Composer:
As with artists, I prefer to tag composers on a last name, first name basis for ease of searching:
Composer: "Bach, Johann Sebastian"
Track Name:
With the hierarchy of Genre - Composer - Artist - Work by artist, I've been able to limit the per-track tags within each album to only that which is required describe the particular element of the work:
Name: "Marcia funebre: Adagio assai" (as the third movement of "Classical - Orchestral", "Beethoven, Ludwig van", "Giulini: Los Angeles Philharmonic Orchestra", "Beethoven: Symphony #3 in E-flat, Op.55 (Giulini)")
Track Numbering
To make this work, it's very important that the track numbering (and disc numbering, for ripped works longer than 1-disc) is correct sequence.
Remaining "Issues"
The biggest problem I find with classical isn't finding the music quickly once it's tagged properly, it's the scarce commodity of the number of characters available to display on the playback device (other than a computer) on car displays, JRemote and Gizmo.
The very limited space available for displaying these values is a big problem for classical music where much more information is required to correctly separate and identify each album and track name than for less tag-data-intensive music, and one reason why using Gizmo in its current form is difficult without having a good memory for the album artwork associated with each album. Even JRemote is somewhat limiting, which is why further solutions are required to enable Gizmo and JRemote to more fully display long tag values for searching and playing.
Track data from metadata download sites is an absolute mess - inconsistent, inaccurate, spelling errors, incorrect capitalization, you name it, it's a disaster. Want consistency amongst your database - there's only one solution...develop a scheme and process, stick to it and do the tagging yourself. Some classical download companies do get this right - Hyperion, Channel Classics and a few others do a good job, but others like Universal's classical store at DeutscheGrammophon.com are downright useless and require full re-tagging of everything with each download.