Hi,
most modern softmods are based upon the font exploit. The font files don't have a signature. When the M$dash loads, it also loads the font files. Some of those are altered in such a way that the Xbox can run unsigned code. This trick leads to the startup of another dashboard like evox or unleashx or xbmc. The whole procedure works without user interaction.
The sound exploit does pretty much the same thing. It uses the database file with the sound track information instead of some font files. At startup, the user has to perform a few actions before the exploit is triggered. In the ndure package, it is used as a rescue method. You can totally disable your softmod. If you won't to switch it on again, you can do so trough the audio exploit. It is a seldom used feature intended for experienced users.
regards.