Ford Sync will automatically connect with paired devices (2013 Focus here). So if you had been playing an audio stream and didn't use one of the music stopping apps, the stream will start playing once it connects. Even more annoying is when you turn the car off and open the door it will start playing again through you phone speakers. So get STOP Music, pin the tile next to your music apps, and tap the tile whenever you finish listening to any music/audio stream. Basically, this happens because WP8 keeps the last audio stream open in the now playing que waiting to be fired up again. It can be annoying.