Just FYI, now that people are gaining rating, there has been a somewhat hidden feature in Total TD since beta that allows players of 300+ rating (Captain) to change the game music at any time. If your rating is 300+, just type any of the following commands in-game to change the soundtrack:

-music terran
-music protoss
-music zerg
-music korhal
-music boss
-music lab
-music space
-music TerranUp
-music juke## (00-13)
-music credits## (01-19)