This report reviewed recent cases of amusia and drew the following conclusions. First, amusia is an ill-defined condition. The classical definition restricted amusia to musical disorders caused by brain lesions. By the end of the last century, however, some researchers included developmental or innate musical disorders in amusia. Second, although recent case reports were based on the classical schema of amusia, there have been an increasing number of case studies that have described more restricted and specific symptoms, such as receptive amusia for harmony or musical alexia for rhythm notation. Third, although we can now obtain more accurate information about the brain lesions, we have not taken advantage of this information. Traditionally, it has been thought that the pitch element of vocal performance is referred to the right frontal or temporal lobe. Lastly, the relationship between musical function and degenerative disease deserves attention. Degenerative diseases can cause either a musical deficit or, paradoxically, improve musical function. For example, the musical competence of some patients improved after selective atrophy of the left hemisphere. In conclusion, recent ideas concerning the relationship between music and the brain have been derived from patients with brain damage, developmental disorders, and degenerative diseases. However, there is a missing link with respect to amusia. We know a lot about the cognitive aspect of music, but the 'true' function of music from an evolutionary perspective, something that is lacking in amusia, is not known.