It turns out that MP3 Retracker was briefly discussed on the ruby-talk mailing list last month. Unfortunately, it fell short of what the posters needed because it doesn't support tagging within Ruby itself (currently it's just a wrapper for the linux-based id3v2 executable).

Doh! Why doesn't someone TELL me these things? The first thing I ever wrote in Ruby was an id3v2 tagger! The kicker is, it didn't work properly (with TXXX tags in particular)- but if there's enough interest I'll dig it up and finish it.

However, it would be way easier just to use someone else's finished id3v2 tagging library (hence the current wrapper). I haven't been able to find anything in pure Ruby that supports both reading and writing, though.

SO: If anyone knows of a fully functional native Ruby id3v2 library, I'd appreciate it if you'd let me know (because then I won't need to write one).