It appears that I can pipe the audio from the MRX to my intercom music input using a patch cord with 2.5mm stereo male on the MRX end and 1/4" stereo male on the music input end. Problem is, the audio cable from my GPS396 already occupies the intercom music input, so I need some sort of "Y-connector" so I can hear both at the same time. Terms like impedance matching and ground looping concern me so fabricating a "Y-connector" may not work, and in fact could damage one or more of the units. Recommendations please?