There's a patch called "BpHpOsc" which produces random fluctuating noises on every note:
http://www24.zippyshare.com/v/81596992/file.html
How did they achieve this modulation? Also, I like the sound, but only the upper-range variation that sounds a couple times in the middle, how do I restrict it? The pitch range is already +/-2 so that's not it. Thanks