MusicBrainz Picard works quite well, it uses the same database as iEatBrainz but is still actively developed. It's free, and I've had great luck with it fixing tags on some 40GB of music I had laying around from my Windows days.
The interface is somewhat arcane unfortunately. Check out this link that will give you some other alternative ideas.
on edit:
I went back to check out the newer version of Picard (0.12 vs 0.11), and the workflow is much improved. A lot of the annoying things from before have been automated. If you take a few minutes to set all the preferences to your tastes using the online help as reference, this really is a great automated tagging app.
iTunes doesn’t seem to exhibit any sort of smart searching built into the search box. Possibly, the best way to deal with these things is to use an external tool.
In my case, I have Coversutra (not free), that allows you to press “tab” (can be changed) to select different things:
I know there are free alternatives that can possibly do the same thing.
An additional alternative could be using an AppleScript and Automator to “ask” for the values… but that might be too much.
tell application "iTunes"
activate
set results to (every file track of playlist "Library" whose name contains “some track" and artist contains “some artist")
repeat with t in results
play t
end repeat
end tell
Something like that, if you can make automator (or the script) to ask you for the two “some” values, you’re set.
My opinion: iTunes should support spotlight like search strings!
UPDATE Ok, you’re right about that one, Coversutra (and others) all use iTunes “syntax” which is… no syntax.
Spotlight, however, is a different beast.
In trying to replicate your scenario, I’ve found that I have two “artists” that are similar in name: Metallica and Metalium. They both contain “Meta” in their names.
So when I search for artist “meta” I get both, which is annoying, because I really don’t like Metalium that much…
So I have two solutions for you:
a. Use Launchbar (or quicksilver), to quickly find the artist (this is a nice way to do it and what I really use most of the time when I want to find a song or an artist, it works faster than anything else). I use Launchbar. Pressing enter there creates a temporary playlist (called Launchbar) that contains all the tracks in question, but you could have dig a little bit more if you wanted an album or song. Very easy.
b. Use Spotlight:
This brings both bands:
kind:mp3 author:meta
but this excludes the unwanted one:
kind:mp3 author:meta NOT author:metalium
Not the best but… what can we do :)
Best Answer
It currently is not possible to add tags in iTunes like you can in other iLife applications. The only reason I can think of why its not available is that most people would just group their music by genre, and that be enough.
Other than using the comments field or the like, there are really not many other options. In some searches I did come across an app called Qloud, but it seems to no longer exist.