If you have an ipad or an iphone you will find that it has the facility to send sound via the thin air (bluetooth) to a unit which is a bluetooth receiver. You can buy bluetooth receivers quite cheaply in Amazon which could be plugged into the back of your keyboard and receive music from your ipad say...providing your ipad is not more than 10 metres away from your keyboard.
What you would need to do is turn on the bluetooth in your iphone or ipad and then link it to whatever bluetooth receiver shows up/is listed on your iphone or ipad.