relay to break audio signal

Hi Guys.  Im simply looking for a diagram.  year and model of vehicle are irrelevant as this is going on a customers house boat.  

The customer has a sony marine head unit with an aux input. I am simply trying to setup his system so that he can use his sattelite radio, and his ipod off of the same aux input. Ive setup a relay with a 2 position toggle switch to break 2 different audio sources before, however, that was years ago, and have since then lost my diagram on how to do the setup. 

Any input or diagrams would be very helpful!