Digital Sound & Music: Concepts, Applications, & Science, Chapter 5, last updated 6/25/2013
At the next step, A3/4 and the 5 node just created can be combined. (We could also combine
A3/4 with E4/5. The choice between the two is arbitrary.) The sum of the instances is 9.
In the next two steps, we combine E4/5 with 9 and then D4 with G4, as shown.
Continuing in this manner, the final tree becomes this: