Amusia: disorders involving music. There are many forms of amusia as there are many elements involved (in music), all concerned with the perception, decoding, and synthesis of sound and time. (Sacks, 99)

Cognitive disorder of “auditory perception” characterized by a reduced ability to perceive information contained in auditory stimuli despite intact “auditory pathways.” Affected individuals have difficulty with speech perception, sound localization, and comprehending the meaning of “inflections” of speech. (MeSH) (Some) patients can hear “timbre” and “rhythm” but not “melody” or vice versa. (Levitin, 194) Also referred to as ‘congenital amusia’ and ‘auditory perceptual disorder.’

Rhythm Deafness: inability to understand rhythm. (May be) slight or profound, congenital or acquired. Forms of rhythm deafness are rarely total, because rhythm is represented widely in the brain. (Sacks, 99)

Tone Deafness: people with such an amusia can veer off key without realizing it, or be unable to recognize off-key singing by others. Present in perhaps five percent of the population. (Sacks, 100) A psychologist discovered a patient who has absolute pitch but is tone deaf. He can name notes perfectly, but he cannot sing. (Levitin, 184)

Total Amusia: tones are not recognized as tones, and music therefore, is not experienced as music. (In a) case in the neurological literature (the authors) describe one man, a former singer, who complained of hearing a screeching car whenever he heard music. (Sacks, 101)