I've had this problem for a while but forgot to mentioned it: sometimes when I go to buy mode to buy stuff (surprised?) and going back to live mode again, the sound from buy mode still plays in live mode, through any other song which sounds extremely horrible.
While trying to get rid of it I go back to the main load screen but even there the music from buy mode plays through the music from the main menu which gives my ears the ugliest sims music remix I've ever heard.
The only thing I could do is existing the game and starting it back again.
Unless some of you know a better way..., which I was secretly hoping for.