Amusia

Language and music are universal and specific to humans. Linguistic and musical proficiency develop in the child spontaneously, without conscious effort or formal instruction.
However, a few individuals suffer from severe language acquisition impairments, which are not associated with any hearing deficiency, mental retardation or lack of environmental stimulation.
Language and music have many similarities and considering these similarities, some individuals suffer from music‐specific impairments.
Music arises as an innate ability that precedes spoken language. It is the art of thinking with sounds.
Infants are sensitive to melodies and are able to distinguish different rhythms.
Babies are sensitive to melodies and rhythms even before birth.
Music is the universal form of language and has occupied a privileged position in all cultures. It is a complex phenomenon and is difficult to describe.
Music, like any sound, is processed in the auditory cortex of cerebral hemispheres of the brain.
Processing of music involves a large network called cortico-subcortical network which is distributed throughout both cerebral hemispheres and the cerebellum of the brain.
If a person cannot recognize differences in pitch, can't sing along with even simple tunes, and can't match the pitch of their voice to the pitch of a piece of music that's being played. Such a condition is said to be tone deaf, which can also be called having amusia.

The term ‘amusia’ was a general term used for the inability to perceive music and it was coined by Steinhals in 1871.
Amusia is extremely rare and it is a permanent impairment of music perception. Amusia does not mean complete absence of musical talent but it is inability to carry a tune. It is the inability to recognize or reproduce musical tones.
A person who is tone-deaf can listen to music but cannot recognize musical tones or reproduce them.
A person with amusia or tone-deaf can listen to music and learn to imitate a tune but due to the lack of musical ability, he is unable to transpose correctly into singing what has been heard.
Amusical persons have no apparent influence on their general intellectual and memory functioning, and they did not report any learning disability other than for music.
(According to Stewart et al (2006), normal music listening comprises 3 components namely, music perception, music cognition, and emotional response.)
Amusia can be considered a central auditory processing disorder due to the lack of appropriate music signal processing in both auditory and cognitive regions of the brain.
Amusia can be congenital (present at birth) or be acquired sometime later in life.
Congenital amusia is an innate music-processing anomaly present since birth. It is the learning disability for music. They have deficits in pitch processing,
This disorder is hereditary and is associated with structural variations in the frontal and temporal lobes of cerebral hemispheres of the brain.
It is a rare and lifelong musical disorder that affects only 1.5% to 4% of the general population.
Congenital amusia is neither caused by a hearing deficiency nor by any form of brain damage or intellectual impairment.
Acquired amusia occurs due to the accidental brain damage in adulthood. Acquired amusia has been associated with damage to different regions in temporal, frontal, parietal, and subcortical regions of the brain.
Patients with brain damage may experience the loss of ability to produce musical sounds.
Characteristics of acquired amusia are the same as congenital amusia but rather than being inherited, it is the result of brain damage. It is more common than congenital amusia.
Patients with acquired amusia who previously enjoyed playing or listening to music may no longer be able to participate in those activities.

Symptoms of Amusia

Symptoms of congenital amusia may be receptive, clinical, or mixed.
Symptoms of Receptive amusia, sometimes referred to as "musical deafness"
Receptive amusia is the inability to identify familiar melodies, the loss of ability to read musical notation, and the inability to notice when a note is out of tune.
Symptom of Clinical amusia is represented by the inability to play a musical instrument, sing, or write music.
Symptoms of Mixed amusia are a combination of the two.

Symptoms of acquired amusia are,

Inability to sing, whistle, or hum a tune (Oral-expressive amusia)
Inability to play a musical instrument (Musical apraxia)
Inability to write music (Musical agraphia)
Inability to read music (Musical alexia)
Inability to recognize songs that were known prior to the injury (Amnesic amusia)

Treatment

Unfortunately, there is no known cure for tone deafness and at present, no forms of treatment have proven effective in treating amusia.

Pitch ear training can improve the sense of pitch through which the notes which are too high (sharp) or low (flat) may be identified.
Audiologists suggest Audiological management which involves explicit auditory training for detecting relative changes in frequency and duration.
Music therapy or singing lessons with a qualified voice teacher may help to regain previous musical abilities or enjoyment of music.

Certain tips to "Tone Deaf" to sing in Tune

Carefully listening to music and using ears to judge or a friend to judge
Recording the song and listening back
Learning to match pitch
Using a Digital tuner or interactive app.
Finding a safe starting note (All singers have a natural range of notes they can comfortably sing, from low to high)
Tuner Training
Gender Swapping