Audio Spectrum using JACK and fftw in C/C++

I am in need of assistance (documentation, sample code, etc.) in how to develop a audio spectrum using JACK and fft开发者_JAVA百科w in C/C++. I am developing on Mac OS X (10.6+). Any help will be much appreciated.

There is a fantastic walkthrough of a jack tutorial here:

http://dis-dot-dat.net/index.cgi?item=/jacktuts/starting/

This should demonstrate how to build a jack application capable of grabbing audio from your system inputs and/or any jack-aware audio player.