A UGen to find the percentile of a signal's magnitude spectrum. Given an FFT chain this calculates the cumulative distribution of the frequency spectrum, and outputs the frequency value which corresponds to the desired percentile. For example, to find the frequency at which 90% of the spectral energy lies below that frequency, you want the 90-percentile, which means the value of percent should be 0.9. The 90-percentile or 95-percentile is often used as a measure of spectral roll-off.

Note that despite running at control-rate, the output remains constant for each FFT frame. E.g. with an FFT size of 1024 and 50% overlap, a new measure is generated every 512 audio frames, or (at control block size 64) every 8 control blocks.