The concept of convergence, from the study of language contact, provides a model for better understanding interactions between cognitive systems of the same type (for example, in bilingualism, subsystem instantiations of the same kind of knowledge representation and its associated processing mechanisms). For a number of reasons, musical ability is the domain that allows for the most interesting comparisons and contrasts with language in this area of research. Both cross-language and cross-musical idiom interactions show a vast array of different kinds of mutual influence, all of which are highly productive, ranging from so-called transfer effects to total replacement (attrition of the replaced subsystem). The study of music contact should also help investigators conceptualize potential structural parallels between separate mental faculties, most importantly, it would seem, between those that appear to share component competence and processing modules in common. The first part of the proposal is to determine if the comparison between the two kinds of convergence (in language and in music) is a useful way of thinking about how properties of each system are similar, analogous, different and so forth. This leads to a more general discussion about the design features of mental faculties, what might define them “narrowly,” for example
