I just checked this little thing
Seems to me that they switch between different wavetable oscillators in the time of the wavelength at key frequency.
In general, one could easily do this using an audio input switch that cycles through the different inputs at the rate of the wave frequency of the triggered midi note. If you now manipulate the different audio streams that are connected to the different audio inputs of the switch, you can edit the different waveform segments separately.
My question: How can I switch between different audio inputs at the rate of a midi note frequency?
Or mighty it be less complicated to just concatenate different wavetables into a wavetable of a length equal to note frequency? What do you think how Waverazor works?