Adding a mechanism to change music is definitely possible and most easy to implement. The catch is adding a trigger since a music event would need to read a string representing the file name of the module to be played. The only place where you can save strings in a level (without hacking it) is the level text array and the properties (next lvl, bonus lvl, etc). Very few events are actually left unused in JCS and I'm guessing jj2 *could* also use a new event mechanism to expand a bit.