System audio in Quartz Composer

Question

I am building a music visualizer in Quartz Composer, and it works just fine. The problem is that the audio input is through a microphone, so any noise that I make while its running displays.

What I want it to do is take only the sound that is running digitally through the system. Not a line input, but whats running through the Mixer AU for output in the system. I haven't found any way to do this except for WireTap, but I don't want a demo and I can't currently afford the full version.

Thanks in advance.