Amusia: The inability to recognize musical tones or to reproduce them. Amusia can be congenital (present at birth) or be acquired sometime later in life (as from brain damage).
It isn’t a problem of the ears – they can understand other sounds perfectly well – but when it comes to music, all tunes sound the same. While most of us are sensitive to small changes in pitch, amusic people need two notes to be very far apart before they hear them as different. It’s no surprise, then, that music, which tends to move in small steps, is literally “lost” on them.
Or just listen to the expert, Dr. Oliver Sacks…