How do I pause a song not just turn the volume off

That depends.And please note that I'm not an EW Support person, only a user attempting to assist other users. It's possible that EW Support Personnel know of a way to accomplish this that I am not aware of.

• If it's a stand alone Video file with audio or a stand alone audio file, the Live Output preview will have a pause button.
• If it's an Audio file attached to song lyric slide you can only mute it. You can't pause it.
• If it's a Video file with audio used as a background you can't pause it, only mute it.