Jelly Roll Morton

Ferdinand Joseph LaMothe was known professionally as Jelly Roll Morton.  He was one of the first people to write down jazz arrangements.  He was able to identify something that musicians were doing and put it into notation in a way that allowed it to be recreated and to re-live.

Questions

This music is not made up (improvised) but there is something about it that sounds fresh.  What is this quality?  How does rhythm relate to it?