XILS 201 is a vintage 20-band vocoder effect modeled after Sennheiser’s vintage VSM 201 Vocoder.
Two filter banks: Each of the two banks offers 20 frequency bands. Each bank of filters can handle an incoming signal (usually a voice signal, but any other signal, including drums) or a CARRIER signal can be processed.
In comparison, the Roland VP-330 had only 10 frequency bands, with a very musical sound but much less definition.