This is a device I picked up from James Newton Howards score to "Nanny McPhee and the Big Bang". Always loved this type of writing so it was fun to try to get the feel right.
As you can see in the score it only consists of 3 elements. The melody and the fills trade off in a call and answer fashion. First time around the violins answer doubled with a marimba at the end of the phrase. The second fill with the celeste and glock is an arpeggiated Cmin/maj7 chord and finally the harp ends with a descending gliss using the C melodic minor scale. Once again the ostinato is there to keep it moving forward without bringing too much attention to itself, and in this case it also acts as a pedal note since it's stays on the tonic C throughout.