by Gary Thieltges of Doggicam Systems was employed, allowing Cuarón to develop the scene as one extended shot. A vehicle was modified to enable seats to tilt and lower actors out of the way of the camera, and the windshield was designed to tilt out of the way to allow camera movement in and out through the front windscreen. A crew of four, including the director of photography and camera operator, rode on the roof. However, the commonly reported statement that the action scenes are continuous shots is not entirely true. Visual effects supervisor Frazer Churchill explains that the effects team had to "combine several takes to create impossibly long shots", where their job was to "create the illusion of a continuous camera move". Once the team was able to create a "seamless blend", they would move on to the next shot. These techniques were important for three continuous shots: the coffee shop explosion in the opening shot, the car ambush, and the battlefield scene. The coffee shop scene was composed of "two different takes shot over two consecutive days"; the car ambush was shot in "six sections and at four different locations over one week and required five seamless digital transitions"; and the battlefield scene "was captured in five separate takes over two locations". Churchill and the Double Negative team created over 160 of these types of effects for the film. In an interview with Variety, Cuarón acknowledged this nature of the "single-shot" action sequences: "Maybe I'm spilling a big secret, but sometimes it's more than what it looks like. The important thing is how you blend everything and how you keep the perception of a fluid choreography through all of these different pieces." Tim Webber of VFX house Framestore CFC was responsible for the three-and-a-half-minute single take of Kee giving birth, helping to choreograph and create the CG effects of the childbirth. Cuarón had originally intended to use an animatronic baby as Kee's child with the exception of the childbirth scene. In the end, two takes were shot, with the second take concealing Clare-Hope Ashitey's legs, replacing them with prosthetic legs. Cuarón was pleased with the results of the effect, and returned to previous shots of the baby in animatronic form, replacing them with Framestore's computer-generated baby. Sound Cuarón used a combination of rock, pop, electronic music, hip-hop and classical music for the film's soundtrack. Ambient sounds of