CDG Editor is a tool that allows the user to edit the contents of a CDG file (typically extracted from a karaoke disc as mp3+g). v1.3 now supports all CD+G command types.
Please note that this is not a Karaoke creation or editing tools (see some of the comments below) - it is for fixing the CDG files that you have where the text is corrupt due to a poor rip from the original CD+G disk. You have to edit individual CD+G tile commands. This tool could be used to change the lyrics of a song...