Pitch shifters take the signal path and shift the pitch, depending on the settings. Most guitar pedals offer a wet/dry mix, with some allowing only wet signal so you can down-tune your guitar pitch without having to re-tune the strings! Most commonly used for adding depth to the sound, the Harmonizer allows the guitarist to add another layer of sound - from one semitone to two octaves - either up, down, or detune. The Octpus goes a step beyond the Harmonizer in range but is less versatile on a pedal board. The Octpus is perfect if you would use your guitar for bass parts, by adding those lower octaves, but can go very high as well which is great fun with vocals.