Getting and frequency decomposition of c# audio stream?

Question

Audio

There is a need to write a program (C#) for light music connected via USB:
1-Intercepting the audio stream of a specific application or a general audio stream.
2-Processing it and decomposing it into a range of frequencies and amplitudes
3-Transferring data to light music
It should be like this:
0-1000Hz-blue
1000-9000Hz-red
9000-20000-green
Amplitude (audio volume) of these frequency ranges should be the brightness of LEDs of a certain brightness.
Tell me any source codes or libraries, or in which direction to dig)