Tunes have always been changed through passage of time and i guess so has lyrics or poems.The written word or a music score has long been kept in transcript.Folk or any other type of artistic expression will always be recorded for the future one way or another.We as creators want this as our legacy for what we have achieved.
So wether it is in the memory,on paper,on vinyl,tape or cd it will remain unique and past on.Nothing set in stone,but from the seed music and song develope.As Lennon said,"never throw anything away." You may need to fall back on that little gem of a line or a tune one day.Get recording them anyway you want.