My singer wrote all of the original songs we are performing. I'm encouraging him to register his copyrights. If he writes the song but the other guitarist writes a great guitar line (however simple it may be) that makes the song come "alive", should the other guitarist get songwriting credit? A real example would be Richard Lloyd's work on Matthew Sweet's "100% Fun". Richard did some really cool guitar parts that made the songs stand out but he doesn't get any songwriting credit. Is this a judgement call or is it standard not to give credit in this situation?