Diegetic and Non-Diegetic Sound in "Heat"

Diegetic sound is sound that is a natural part of the scene or narrative, such as sound effects. Non-diegetic sound is sound that is not a natural part, for example music. In the bank heist scene from "Heat", everything is going as they had planned it for the first couple of minutes. There is the non-diegetic sound of a cool, slick soundtrack as De Niro and his crew go in, hold the place up, control the crowd, get into the vault and take the money with no hinderances or setbacks. But when they come out and Pacino and the LAPD move in, it cuts to silence. This represents a hitch in the plan, and how everything will go downhill from here. Pacino's plan to make some simple arrests also goes awry as the crew open fire on them. The only sound here is the diegetic gunfire in the ensuing shootout. This also portrays the firefight in the most gritty and realistic way possible, as if this gunfight were real, there would be no non-diegetic sound, and all that would be hear is the gunfire. There is also an extended silence when Pacino is aiming at the man who has taken a child hostage, which creates suspense as there's a good chance he could miss his target and hit the kid. The lack of soundtrack and non-diegetic sound also adds more impact and punch to the more powerful uses of diegetic sound, like each death or car crash.