Hello, A little back story first.
I formed an amazing band, full of wonderfully talented people and fun to be around people and we all get along great. Never a band fight or any drama. A couple of weeks ago we brought on a rhythm guitarist, I play most of the guitar parts but an extra hand to help fill out the sound was appreciated. His job was simple, all he had to do was play. I wrote and composed ALL the songs and instrument parts. He had to only play the parts I showed him. And it went well.
We decided that the band was doing so well that we would do a professional recording of one of our better songs to see what would come of it. maybe get lucky. So the band all pitched in about a 100 dollars apiece to buy some recording time at a local studio. Our jobs only permitted us to do some quick recording on weekends so the studio time has been spread out over the course of a month, we are done with all the instrument parts and will be starting with vocals next week.
Now here's the problem. Turns out the guy we brought on the play rythem had some serious closeted dramatic tendencies. This guy is like Alex Roses reincarnation. He is more prima donna than our female lead singer, who is actually pretty chill and cool, and he's just a rhythm guitarist.
So the band has decided to part ways with him, as he was just there as a helping hand anyways.
Now, should we re-record his rhythm parts to prevent copyright problems in the future? We have no contract or anything but I would hate for the song to get big and this low and behold this guy comes calling for a couple of chords he put down, even if i wrote them?
also, would giving him his 100 he pitched in for studio time back(which we were going to do anyways) relieve us of any obligations to him.
We just want nothing more to do with the guy now or in the future and don't want any ticking time bombs laying around.
You don't need to re-record his parts for copyright purposes. If you wrote everything you hold all of the copyright. He holds zero. However as he has currently chipped in cash he is part owner of the actual recording so you should opt to pay him back/buy back his share.

When you do so also write out something that both of you sign that states something like "in exchange for $100 I [Rhythm Guitarist] forfiet any copyright or property claim I may have in relation to the recording". We had a bad breakup with a member in a previous band where that happened.
And no, Guitar Hero will not help. Even on expert. Really.