They say:

Meet the new BOSS harmonist, with four intelligent pitch-shift effects and three-voice harmony in one convenient unit. Among the effect modes are Harmony, Pitch Shifter, and Detune, plus the all-new Super Bend for authentic pedal-bending effects and wild three- and four-octave pitch sweeps. You can even control pitch with an optional expression pedal. The harmony function is fast and simple to use, and supports a variety of interval patterns. It’s easy to create rich, three-voice harmony: choose a major or minor key, and set SHIFT to 3-VOICE—that’s it! The PS-6 Harmonist is an unbeatable combination of superior sound quality, ease of use, and powerful pitch effects, all under one hood.