Vokko is a stereo vocoder, It supports stereo inputs so you can use stereo modulators and it process all signal internally in stereo so you can also use stereo carriers. Basically this plugin processes left and right signals in parallel using two imbedded "MDA Talkbox" vocoders and two separate filters.
Stereo operation is very uncommon, and very handy because you can vocode two signals with rich stereo content, for example you could vocode a voice with a stereo wide moving pad (a la wavestation)
It has inbuild soundfont players so you can use all those beautiful pad soundfonts around, also it has an analog style synthesiser if you want simple waveforms like a sawtooth/pulse as carrier to make cheese ;) with Vokko you dont have to mess around with panned external signals to feed the vocoder, just load it, feed audio, MIDI and you're done.
Two filters in parallel (A and B) allows you to apply a LP/HP/BP/BR filter mode, you can control the timbres and/or panning separately for each vocoder.It also features pitch tracking and extensive LFO.