Audio Frame rate independent way of collecting spectrum data over fixed intervals of time

Hey Everyone,

I'm trying to figure out a way to call the GetSpectrumData function on a given AudioSource in a very short but fixed time period. I have tried doing this in the update function, which is very slow and imprecise for audio, I've tried using coroutines, and I've tried using InvokeRepeating. I believe all of these methods are frame rate dependent, and I am wondering if there is a way to do this easily that I just haven't found yet. I am hoping to get something that executes every millisecond. Does anybody know of a way to do this? Thanks.