I have to confess that I have pretty much no idea how the filter works or the math behind it. I wrote that part with a friend who has some DSP background but it

I have to confess that I have pretty much no idea how the filter works or the math behind it. I wrote that part with a friend who has some DSP background but it was essentially copied from a signal processing book :) But it sounds alright and was easy to implement, I can see why it's popular.