Angels (Ideas for a prologue)

I recently finished the musical I've been working on and starting writing this as a potential prologue to another one. I got about this far, but am unsure where to really go with it from here. 

Difficult. Reminiscent of Terry Riley or Mike Nyman who would continue in the same vein until a need for change or the end occurred. Possibly you could bring in/fade in more sustained material around it if intending a change of tempo. Or possibly emphasising notes to form a rhythm to extract new material from the fragment based on the accented notes? 

I agree with Quinn, but other possible solution could be a really constrating section there that eventually evolves to the main material, or either holds the constrast. As it's a prologue, I belive the fact that the feeling of something more coming: "this is just the start" is precisely the most indicated one.