I am not sure how you are going to implement this, but it is a wonderful idea. You can record different numbers/extensions off your regular phone, for different songs and play the song according to the number you pressed. Please share it with us if possible.
I don't think your intent was much like the OP's, but maybe you should look at Modem::Vbox. There is also a module for complete IVR (Interactive Voice Response) systems: Ivrs =)