In the film, Children of Men, how is sound portrayed in the cease fire scene?

In the movie Children of Men, during the "miracle cease fire scene," there is a certain religiosity to the music. It is as though angels are singing praises to the newborn child, much as the heavens rejoiced when Jesus was born as portrayed in many recreations of the Nativity in Christianity. While this joyful hymn is sung by sopranos, the warfare stops, and even some of the soldiers make the sign of the cross when Theo and Kee pass by them with the crying newborn girl. At the sound of the baby's cries, cries not heard for nearly two decades, the fighting ceases and people look with reverence and awe at the mother and her newborn.
This dystopian story begins with the death of the youngest person in the world, a young man of eighteen. Much of the world is unlivable, and many refugees try to enter the United Kingdom. One immigrant rights group, the Fishes, is led by the estranged wife of the main character, Theo Faron. Named Julian Taylor, she offers Theo money if he will acquire transit papers for the refugee, who is named Kee. Theo obtains these papers from his old friend Nigel, who is a wealthy government minister, while also learning that the papers come with the stipulation that someone accompany the refugee. Offered a substantial payment, Theo takes the job.
There is treachery in the Fishes organization, however, and Julian is murdered as Theo and Julian, the midwife Miriam, and Kee head to the coast. Theo breaks down from the loss of Julian, but he stays with Kee.
Problems occur after Julian dies. Theo learns that his estranged wife has been cruelly murdered by Luke, who intends to use the baby for political reasons and kill Theo. So Theo takes Kee and Miriam in a car to his friend Jasper, a former political cartoonist, who has become a pot dealer. Jasper knows a guard to whom he sells marijuana who will smuggle Theo and Kee into Bexhill-on-Sea as refugees. Unfortunately, the Fishes find Jasper and murder him; Theo and Kee flee. They hide in an abandoned schoolhouse and wait for a prison guard named Syd who transports them. Miriam tells Theo about the abandoned school:

"...as the sound of the playgrounds faded, the despair set in. Very odd, what happens in a world without children's voices."

On the bus Kee's contractions begin, so Miriam distracts a guard by feigning mental disturbance. However, she is removed and a hood placed over her head. Soon, the baby is born in a room at the camp. Having learned that Theo and Kee have a bounty on their heads, the guard Syd tries to capture them in his greed, but Theo and the woman who has provided them the room fight him off. In the meantime, the Fishes have captured Kee and the baby, but Theo rescues them and they make their escape. Their passage through a virtual war zone occurs because the warring British army and the refugees become so awestruck at hearing the newborn's crying that they cease fire as the group passes through their ranks. The music and singing reflect this awe, and there is also a sense of rejoicing in the angelic voices that sing in a hymnal fashion.
http://www.dailyscript.com/scripts/children_of_men-script.pdf