Apocalypse Now - Sound Analysis

At the beginning of the Apocalypse Now video, we instantly get an on-scene diegetic sound, with the noise of the propellers from the helicopter spinning around, and the sound getting slightly louder as the propellers get quicker. As they helicopters leave and start flying above the trees, music from off the scene becomes involved, and this is a contrapuntal sound, as it isn't relevant to what is happening in the scene.
A short while later in the time 3:33, music starts again but this time its a parallel sound, as the music starts of slow as the helicopters come together in preparation to attack the oncoming land. During the attack, many disoriented sounds are heard, as you quietly hear people shouting and screaming off the scene, and hearing bombs exploding either far away so the sound is quiet and muffled, or on the actual screen so the sound is much louder.