Have the radio play every time you turn on the lights in the bathroom. Make sure to turn off the lights and also the circuit breakers to prevent electrocution! Just patch in your old alarm clock that you don't use anymore and viola! Auto music every time your turn on your lights!
Most alarm clocks may require you to push a on button after plugging it in. You need the kind that just turns on as soon as you plug it in. In other words, the dumb ones that switches on with a mechanical switch or slider.