MILES to GO || before I sleep

Before my iPad 2 arrives (or at the very least, before iOS 5 comes out in September), I want to get my iTunes library sorted out.

At some point in the past, I deleted chunks of my library somehow, and I either ended up with "MIA" files that iTunes didn't know how to locate, or songs that were just plain missing. Occasionally I would look at a massive copy of my iTunes library that I'd put on one of my external drives and try to find different songs, but it was a lot of work and I didn't get very far.

Enter Dupin. It's a piece of software for weeding out duplicates, even more specifically than iTunes does from its own File > Display Duplicates menu option. I decided to dump everything from my external hard drive and sort it out using Dupin.

And for the most part, it's been okay--I try to match songs using Name, Artist, and Time, because kind (mp3, m4a, m4p, etc.) can be different, and Album might be different if I've imported the song from multiple albums (which happens when I have singles and full albums, or Best Of/Greatest Hits albums in addition to either of the other two).

It was still a pain in the ass. Before I officially deleted anything, I still had to compare that what I had deleted was what I actually WANTED to delete--anything with a lower bit-rate, a protected file, or that was confirmed to be EXACTLY the same as something I already had in my library. Sometimes artists will release a song a second time, not change anything about the title, but extend the song out, remix it, etc. You have to listen to it very carefully to know the difference(s), and that takes time.

I opted to start using beaTunes 3, which allows you to clean up your music library using a LOT of other factors, including sorting issues. And this begs the underlying question: just what fields are important to have for your music?

See, I have lots of albums by multiple artists, e.g. Singer, but also Singer feat. Singer 2. Normally I'd tag these as Compilations, but apparently they're not--if Singer is in the beginning of the Artist field, then Singer feat. Singer 2 is regarded as the same. I don't want to put the "feat. Singer 2" in the Track Title, because in my mind, that's not accurate. The artist is asking about who is behind the song: the vocals, the instrumentals, what-have-you. That doesn't belong in the song title.

But iTunes has all these other metadata fields you can sort by, including Sort Artist and Album Artist. The question is, do I type the artists like I have normally (First Last), or do I type (Last, First feat. First Last 2), kind of like I would be if I were compiling a Works Cited list for a paper? Do I list Singer feat. Singer 2 as (Singer, Singer 2) instead? What exactly is the hierarchy for these sorts?

I get the impression that a track has Artist, but Sort Artist can dominate that, and Album Artist dominates both of those. Does that sound about right?

And if Compilation only matters when you have different Artists (not Sort Artists? Not Album Artists?), and it automatically organizes the tracks by Album instead, then I should be using Grouping instead for my fanmixes, right? Or just make regular playlists, instead of Smart Playlists?

Help!