Crazy88Fingers

Okay, I've got a good one for you guys. My band recorded a demo song last year. I just got the copyright certificate in the mail today. Here's the problem. The copyright has two of the old band members' names on it. Now we're about to record a new EP that includes the old demo song, and want them off the copyright. We have new members and all the old members' work is no longer being used (they only contributed their individual tracks). So how do we go about doing that? Can we just re-copyright the new recordings? What's the easiest way to go about this? Also, can I copyright individual parts of the songs? Like my keyboard tracks? I'm not sure if I explained it well enough. But thanks in advance.