This device was developed for MIDI keyboard control of the TET Trigger Player.
The weirdness of the "transcription error transposition" pitch-shifting algorithm means that it requires two controls, to raise and drop (often in combination) sample pitch. This MIDI Interface automates those controls by auto-calculating raise/drop ratios that correspond to semitone transpositions (2 octave range, repeated across the keyboard) and sending them via CV, while also providing note on/off events via a gate output. Basically, after connecting a few wires, you can play a sample on a keyboard through the TET process to great effect.
This device controls one sample lane (out of the 6 provided on the TET Trigger Player), but you can use multiple units, split from the the same MIDI source, to connect multiple lanes. With the gold min/max dials (above the MIDI IN jack), you can specify note ranges for each MIDI Interface and consequently for each connected sample lane.
Why bother? Because TET pitch-shifting sounds super interesting, filled with artifacts and bit off in the right way. Now, you can readily apply it to samples to melodic ends.