id321 is a command line ID3 tag manipulation tool. It supports reading and writing of ID3 tags of the following versions: ID3v1, ID3v1.1, ID3v1.2, ID3v1.3, enhanced tag, ID3v2.2, ID3v2.3, and ID3v2.4. The utility can force standards of ID3 tags in order to fix existing non-standard tags.
Rippix is a fork of ripperX, a fast and easy to use CD ripper. While ripperX does a good job of ripping and encoding songs from a CD, it uses a rather outdated user interface. Rippix tries to fill this gap. This includes porting Rippix to GTK+ 3. Additionally, a lot of deprecated code will be rewritten and documentation will be added. The reason for a fork is that after some hacking on the ripperX code, it appeared that more modifications were necessary in order to port to GTK+ 3 conveniently than what could be appreciable by ripperX devs, like removing all the XPM images (including the logo) from the UI.
SQL Tagger reads the tags of audio files from a directory, loads them into a temporary SQLite database, accepts SQL queries to modify this database, then saves any changes back to the audio files. It's useful for performing complex updates that would be difficult or tedious with conventional taggers. It's a complement to conventional taggers, not a replacement.