Something like this needs to be sorted out right at the start.The only genuine millionaire rock star I know - Ian Dench of EMF - did advise me on this.He had a 90% cut of the publishing and copyright,largely because he contributed 90% of the work.He is now a very wealthy man.The rest of EMF aren't.My understanding is that copyright exists automatically upon recording,(sound or written down) so if none of your old ( or current) bands material was recorded then no copyright exists,so anyone can do with it what they wish.There's plenty of examples of ex band members claiming their share of royalties,and failing,the afore mentioned Smiths rythm section,Spandau Ballet spring to mind,and of course Nirvana.If you're writing original material,get the legal aspect sorted asap..