Pitch constancy refers to the ability to perceive pitch identity across changes in acoustical properties, such as loudness, temporal envelope, or timbre.[1] The importance of cortical regions lateral to A1 for pitch coding is also supported by studies of human cortical lesions and functional magnetic resonance imaging (fMRI) of the brain.[20][21][22] These data suggest a hierarchical system for pitch processing, with more abstract properties of sound stimulus processed further along the processing pathways.