Get Audio from Speakers

Hello,

I'm wondering if it is possible to take audio from a different program, such as spotify, or itunes and route it into Unity. And then, if this is possible, will I be able to perform FFTs on that audio as if I uploaded a song directly into Unity? What options are there regarding this type of problem?

In essence, what I want to be able to do is analyse sound coming from the speakers and execute a visual effect in reaction to the audio. Any ideas?

Thanks!