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.
As a result of this defect in pitch perception, a lifelong musical impairment may emerge due to a failure to internalize musical scales. A lack of fine-grained pitch discrimination makes it extremely difficult for amusics to enjoy and appreciate music, which consists largely of small pitch changes.Tone-deaf people seem to be disabled only when it comes to music as they can fully interpret the prosody or intonation of human speech. Tone deafness has a strong negative correlation with belonging to societies with tonal languages. This could be evidence that the ability to reproduce and distinguish between notes may be a learned skill; conversely, it may suggest that the genetic predisposition towards accurate pitch discrimination may influence the linguistic development of a population towards tonality. A correlation between allele frequencies and linguistic typological features has been recently discovered, supporting the latter hypothesis.Tone deafness is also associated with other musical-specific impairments such as the inability to keep time with music (beat deafness, or the lack of rhythm), or the inability to remember or recognize a song. These disabilities can appear separately, but some research shows that they are more likely to appear in tone-deaf people. Experienced musicians, such as W. A. Mathieu, have addressed tone deafness in adults as correctable with training. Acquired amusia
Acquired amusia is a musical disability that shares the same characteristics as congenital amusia, but rather than being inherited, it is the result of brain damage. It is also more common than congenital amusia.