I have written a simple library for harnessing the FFT analysis built into Sonia. It is very useful for VJ use, I just used it on the Generator.x concert tour with success.

Basically it keeps track of the recent maximum values, and uses them to normalize the input so that you will get a predictable range of values. It also uses a very simple dampening mechanism to get more harmonious results. I will post it here as a library in the immediate future.