From TC Elctronic:

With one of their newest offerings, TC have done something truly wonderful. For those looking for a standard sized, diatonic harmonizer, the only real option, for years, was the Boss PS-6. TC Electronic has entered the harmonizer game with the Quintessence, and have done so in a big way. This new pedal features a simple interface, beautiful sounds, next-level tracking speed. There are few, if any, harmonizers in its class that can match up. Do you want tight sounding harmonies in any key with a multitude of scale and voicing options? Then go get yourself one of these babies