First off, WELCOME TO NICOclub! Glad to have you here as part of the Murano forum!!!
I don't believe you need the remote, the sound is probably being currently fed through the head sets (which you don't have). On my Armada the audio is controlled on the dash through the stereo. I would try some of the stereo buttons, either an AUX button, or something like that. Please let me know if that helps at all.
You can also view your owner's manual for the '05 Murano here if you don't already have it:
http://x.nissanhelp.com/forums...ks/48