Amusia can be diagnosed using a battery of tests, the Montreal Battery for the Evaluation of Amusia (MBEA; Peretz, 2003). The first documented case of congenital amusia in childhood is described in the paper listed below. Amusia is one of a number of disorders of perception that I have written about in this blog, including prosopagnosia and agnosia for scenes, that have been theorized as being caused by a lack of connections in the brain, which could be seen as the opposite of synaesthesia. I guess that amusia, a difficulty in perceiving music, could be seen as the opposite of perfect pitch, which is an ability that appears to be associated with synaesthesia and autism.
Marie-Andrée Lebrun, Patricia Moreau, Andréane McNally-Gagnon, Geneviève Mignault Goulet & Isabelle Peretz Congenital amusia in childhood: A case study. Cortex. (article in press) doi:10.1016/j.cortex.2011.02.018 http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B8JH1-529MVTS-1&_user=10&_coverDate=03/04/2011&_rdoc=1&_fmt=high&_orig=gateway&_origin=gateway&_sort=d&_docanchor=&view=c&_searchStrId=1726989201&_rerunOrigin=scholar.google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=43fef257d6f2b1bfce00e36d3badb560&searchtype=a
Lauren Stewart Congenital amusia (quick guide) Current Biology. Volume 16 Issue 21 7 November 2006. Pages R904-R906. doi:10.1016/j.cub.2006.09.054 http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VRT-4M8WTCF-7&_user=10&_coverDate=11%2F07%2F2006&_rdoc=20&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info(%23toc%236243%232006%23999839978%23636547%23FLA%23display%23Volume)&_cdi=6243&_sort=d&_docanchor=&view=c&_ct=32&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=7d8218bc925dd41d5cb5c44a89ac76b4&searchtype=a
Delosis Research Technology Musical Listening Test http://www.delosis.com/listening/home.html