In 1888–1890, August Knoblauch produced a cognitive model for music processing and termed it amusia. This model for music processing was the earliest produced.While the possibility that certain individuals may be born with musical deficits is not a new notion, the first documented case of congenital amusia was published only in 2002. The study was conducted with a female volunteer, referred to as Monica, who declared herself to be musically impaired in response to an advertisement in the newspaper. Monica had no psychiatric or neurological history, nor did she have any hearing loss. MRI scans showed no abnormalities. Monica also scored above average on a standard intelligence test, and her working memory was evaluated and found to be normal. However, Monica had a lifelong inability to recognize or perceive music, which had persisted even after involvement with music through church choir and band during her childhood and teenage years. Monica said that she does not enjoy listening to music because, to her, it sounded like noise and evoked a stressful response. In order to determine if Monicas disorder was amusia, she was subjected to the MBEA series of tests. One of the tests dealt with Monicas difficulties in discriminating pitch variations in sequential notes. In this test, a pair of melodies was played, and Monica was asked if the second melody in the pair contained a wrong note. Monicas score on this test was well below the average score generated by the control group.
Amusia is a musical disorder that appears mainly as a defect in processing pitch but also encompasses musical memory and recognition. Two main classifications of amusia exist: acquired amusia, which occurs as a result of brain damage, and congenital amusia, which results from a music-processing anomaly present since birth. Studies have shown that congenital amusia is a deficit in fine-grained pitch discrimination and that 4% of the population has this disorder. Acquired amusia may take several forms. Patients with brain damage may experience the loss of ability to produce musical sounds while sparing speech, much like aphasics lose speech selectively but can sometimes still sing. Other forms of amusia may affect specific sub-processes of music processing. Current research has demonstrated dissociations between rhythm melody and emotional processing of music. Amusia may include impairment of any combination of these skill sets. Signs and symptoms
Symptoms of amusia are generally categorized as receptive, clinical, or mixed. Symptoms of receptive amusia, sometimes referred to as "musical deafness" or "tone deafness", include the inability to recognize familiar melodies, the loss of ability to read musical notation, and the inability to detect wrong or out-of tune notes. Clinical, or expressive, symptoms include the loss of ability to sing, write musical notation, and/or play an instrument. A mixed disorder is a combination of expressive and receptive impairment.Clinical symptoms of acquired amusia are much more variable than those of congenital amusia and are determined by the location and nature of the lesion.