In acquired amusia, inability to perceive music correlates with an inability to perform other higher-level functions. In this case, as musical ability improves, so too do the higher cognitive functions which suggests that musical ability is closely related to these higher-level functions, such as memory and learning, mental flexibility, and semantic fluency.Amusia can also be related to aprosody, a disorder in which the persons speech is affected, becoming extremely monotonous. It has been found that both amusia and aprosody can arise from seizures occurring in the non-dominant hemisphere. They can also both arise from lesions to the brain, as can Brocas aphasia come about simultaneously with amusia from injury. There is a relation between musical abilities and the components of speech; however, it is not understood very well. Diagnosis
The diagnosis of amusia requires multiple investigative tools all described in the Montreal Protocol for Identification of Amusia. This protocol has at its center the Montreal Battery of Evaluation of Amusia (MBEA), which involves a series of tests that evaluate the use of musical characteristics known to contribute to the memory and perception of conventional music, but the protocol also allow for the ruling out of other conditions that can explain the clinical signs observed. The battery comprises six subtests which assess the ability to discriminate pitch contour, musical scales, pitch intervals, rhythm, meter, and memory.
While a method of treatment for people with amusia has not been defined, tone differentiation techniques have been used on amusic patients with some success. It was found with this research that children reacted positively to these tone differentiation techniques, while adults found the training annoying. However, further research in this direction would aid in determining if this would be a viable treatment option for people with amusia. Additional research can also serve to indicate which processing component in the brain is essential for normal music development. Also, it would be extremely beneficial to investigate musical learning in relation to amusia since this could provide valuable insights into other forms of learning disabilities such as dysphasia and dyslexia. Notable cases
In fiction
Horatio Hornblower
Grace from Home on the Range
James Fraser from Outlander by Diana Gabaldon
Rodrigo from Mozart in the Jungle

See also
Absolute pitch, the human ability to name a musical note when played or sung (less common than relative pitch)
Auditory agnosia
Cognitive neuroscience of music
Color blindness
Musical aptitude
Music-specific disorders
Relative pitch, the human ability to accurately distinguish pitch intervals (more common than absolute pitch)
Synesthesia
Tonal memory

References
Further reading
Kazez D (1985). "The myth of tone deafness". Music Educators Journal. 71 (8): 46–47. doi:10.2307/3396499. JSTOR 3396499. S2CID 144988256. Kleist, Karl (1962). Sensory aphasia and amusia; the myeloarchitectonic basis. Oxford: Pergamon Press. OCLC 1649635. External links
MedicineNet: Amusia
NIH: Distorted Tunes Test
The Listening Book: Tone-Deaf Choir audio description by W. A. Mathieu