hD is a distortion effect with harmonic generators. It can generate two pitch-shifted copies of up to two octaves above the input signal - the volume level of the two voices can be set independently. hD also has a sub-octave generator. hD's design uses its harmonic generators to enhance the distortion. The two harmonic voices are mixed into the signal before the distortion stage. The sub-octave generator algorithm was developed specifically for hD. It is latency-free. hD can also be used to generate 12-string guitar effects and as a note doubler.