Brendan Quinn and Margaret Hanley (learned BBC colleagues, both) point me to an interesting discussion around classical music metadata, or rather the lack of it, in iTunes etc., over at the TidBITS Talk list.
As a classical music listener, of a kind, and a heavy-duty iTunes user, I've long struggled with this. iTunes4 did begin to add 'composer' tags etc., but I'm then forced to put lots of other info in to the 'comments' box (conductor, soloist etc.). The track names vary massively - I don't have a consistent format (that I can remember, anyway) for marking out movements, suites etc.
We built a separate interface to our classical artist/album database at BBCi Music, based around Amazon's existing design pattern (and the advice our 'classical experts' at BBCi Music) here (please ignore the visual design; needs a facelift). Check the advanced album search.
This doesn't even touch things like 'movement', which the TidBits discussion refers to. It's a fiendishly complex area.