These guys built on the pressure wave model but using quite resonant formant filtering of the chirp impulse and noise. The spectrum is taken from a woody/carboard pallete, because that's what fireworks are made of, and a little bit of the ripper (chaotic oscillator) is mixed in, depending on the distance to make them seem sharper up close.
The listener is close to the source of the rockets. There is a delay for when each rocket is fired, until it reaches a height. The higher it goes the further it is away from you when it explodes. Nearby are some buildings from which echos emerge. In a similar way to the thunder patches we have filtered the reflections and delayed different frequencies to create a coherent distance effect as the range in increased.
To make a convincing demonstration a random fireworks generator launches rockets in bursts so that you can hear the range of slightly random colours and delay effects as the positions and reflections interact. This effect is based on listening to a recording of fireworks in an urban/city street, we would choose different environment variables to simulate trees or a more open terrain.
All the parameters are collected into a single behaviour called "distance" on one slider.