It's often interesting to look through the search queries this site gets to see what people are looking for. Over the past few months the phrase "delete all lyrics" has been showing up pretty frequently. Don't know why it isseems like it wasn't so long ago the phrase "find song lyrics" was more prominent. Fads! Who can predict 'em?
I already have a script that will delete the lyrics of a selection of tracks. But this would be rather slow if you used it against every track in the library. So I've posted Delete All Lyrics. This is a Cocoa-AppleScript applet (for OS 10.6 and 10.7 only) that will fairly quickly go through all the tracks in the "Music" playlist and delete the lyrics. So whether you're tired of trying to sing-along or just need to clear out some bytes, it should do the trick.