Medley (Ar tonelico Qoga)

A Medley, or Half Reyvateil (半レ人) is term that was coined by Tyria as a partially serious joke to refer to Aoto's particular conditions. However, the term does have a more deep significance. A Medley is basically a human male that has active Reyvateil genes, in contrast to the normal ones who have them supressed. Still, due to the Y-Chromosome not resonating correctly with the Reyvateil genes, they can't yet still connect to any of the SH Servers nor use Song Magic.

However, if they tried to undergo the necessary process needed to connect them to an SH Server, which is a particularly large emotional shock, or a traumatic event, their H-Waves would grow much stronger, so much that they would reach the point in which their mind would be unable to bear with the strain, and would completely collapse, leaving them as empty shells that do nothing else than to kill and prey on other humans. This condition is known as the Border Disease. Both the Medley condition, and the Border Disease are only found in the region of Sol Cluster.

The reason why the Reyvateil genes happen to be active on a large part of the human population of Sol Cluster is because of the preparatives the Archia Think Tank made for the execution of their Human Evolution Project, which consisted in spreading among experimental subjects modified Reyvateil genes, so them and their offsprings could be merged with the Antibodies in a much easier way.