he uses symbolism, when Bridie recounts the concert the Japanese held for the prisoners she recounts how all the women realized they were going to live and how they all "looked at the SKY the CLOUDS and the BIRDS", The Sky and birds represent the freedom and unity the women gained through the music, shows how they survived ( links with the choir and sonata) while clouds shows the light and happy feeling
also uses stage directions , when Sheila recounts the liberation from Belalau it says that "Bridie takes sheila's hand", its the physical manifestation of their friendship and how it supported them and helped them to survive.
There are more but i really have to go sleep now
GOOD LUCK!