I have been fully immersed in a project to tag a big library of classical music properly. It has been a real eye opener - both by the amount of work necessary and by the prehistoric nature of the state of the art.
Tags are one of the most critical components to building a library. For those unfamiliar with tags, they are the metadata that allows our machines to sort our music - artist, track title - composer - etc.
Imagine walking into a record shop and there's a pile of 1000 albums sitting on the floor in no order at all. You couldn't find anything without looking at everything. That's the importance of tags.
In fact, the entire experience with any kind of user interface like iTunes, eLyric, Sonos, Sooloos all depend on the quality of the tags. If you misspell Beethoven the program has a hard time finding him. Or perhaps you have some tracks listed as Beethoven - Ludwig Beethoven - Ludwig Van Beethoven - Beethoven, Ludwig - etc. You get the idea.
The biggest key to tagging is consistency. If you're building a library, remember to be consisten in all your tagging and you'll be ok.
