before the bible existed it was quite likely that everything in the bible was passed down through spoken word. in order to make these stories easier to remember they were likely passed down through song. the reasoning behind why stories were passed down through song is because it is easier to remember something when it is learned in more than one way. the easiest way we can see it is when we get a song stuck in our head or are able to remember the lyrics to a song after hearing some of the notes from it. that is one of the reasons why the bible stories were passed down through song.