<P> Speakers of European languages have been found to make subconscious use of an absolute pitch memory when speaking . </P> <P> Absolute pitch is the ability to perceive pitch class and to mentally categorize sounds according to perceived pitch class . A pitch class is a set of all pitches that are a whole number of octaves apart . While the boundaries of musical pitch categories vary among human cultures, the recognition of octave relationships is a natural characteristic of the mammalian auditory system . Accordingly, absolute pitch is not the ability to estimate a pitch value from the dimension of pitch evoking frequency (30--5000 Hz), but to identify a pitch class category within the dimension of pitch class (e.g., C-C ♯ - D...B-C). </P> <P> An absolute listener's sense of hearing is typically no keener than that of a non-absolute ("normal") listener . Absolute pitch does not depend upon a refined ability to perceive and discriminate gradations of sound frequencies, but upon detecting and categorizing a subjective perceptual quality typically referred to as "chroma". The two tasks--of identification (recognizing and naming a pitch) and discrimination (detecting changes or differences in rate of vibration)--are accomplished with different brain mechanisms . </P> <P> The prevalence of absolute pitch is higher among those who are blind from birth as a result of optic nerve hypoplasia . </P>

Cultural variations play out along a spectrum and are not absolute