4-band (octave) distortion implemented using polyphase IIR all-pass second-order up and down samplers.
Each octave frequency band has a different distortion process (created from the Large gain followed by the Audio Clipper).
This is a good example of multi-rate signal processing whereby high computational efficiency can be achieved by
successively downsampling the signal such that the processing in each "band" is running at a successively lower sample
rate. In this example, each band is an octave lower than the previous (due to the factor of 2 downsampling). The
downsamplers are implemented using 2-channel recursive filter banks (consisting of complementary hi - lo allpass filters
implemented in polyphase form). This is the most efficient method of implementing the filter banks. (However, since these
IIR filters do not exhibit linear-phase characteristics they may be unacceptable in some applications.) This DrawingBoard
clearly illustrates the powerful multi-rate functionality of WaveWarp, a key feature of the software. Try out different effects in
the various frequency bands !
