Answer:
The sharp slim blade, that cuts the wind. What is it?
You heard me before, yet you hear me again, then I die. Until you call me again.
Don't do this in the shallow end.
According to the music industry, you can count on a midnight train and the devil to turn up here.
I pass before the sun, but make no shadow.
I repeat only the last word you say. The more I repeat, the softer I got. I cannot be seen but can be heard. What am I?