dynamic audio measuring?

Hello, I am working on a music visualizer type effect for my game. I am using something like this to measure the pitch and volume:

(audio.volume > .5) what ever the function is, etc...

But Ive run into a problem. Since the audio pitch and volume is set in the audio source inspector/code, it remains constant (so if I set the audio volume to .5. even if in the song there is a sudden increase in sound in the actual song, nothing will happen). How can I remedy this?

Also, is there anyway to measure a sudden increase in volume/pitch regardless of the numbers?

Thank you, I know this is an odd question.