Mac OS X only: Free beta application Pollux analyzes the audio fingerprint of tracks in your music library and corrects the song's title, artist, album, art, lyrics, and more. It's simple to use and it works very well.
While this sort of automated metadata fixing is one of the five big features we want to see added to iTunes, it's not something we're expecting from Apple any time soon. Pollux isn't the first to tackle this territory, by any means, and in the past I've highlightedTuneUp as my favorite tool of this ilk, so the first thing I wondered was: How does Pollux stack up to TuneUp?
To find out, I pointed Pollux at a handful tracks that TuneUp has always had trouble identifying for me. The results: Pollux was able to successfully tag a few of the tracks that TuneUp was lost on. That doesn't necessarily mean that Pollux would have been able to identify all of the tracks that TuneUp was able to in the past, but it does bode well for thefree Pollux. (TuneUp comes in a limited free version, but requires some money for full functionality.) I also pointed it at some tracks TuneUp had successfully tagged and found it batting a thousand there.
Pollux works in a couple of ways: Either you can tell it to automatically analyze and tag any new files you add to iTunes (which makes it simple and unobtrusive), or you can select individual tracks, click its menubar icon, and click Tag Selected iTunes Tracks.
Pollux is freeware (donations accepted), Mac OS X only; for the money, it seems like the best tool of its kind right now.