On a related issue of timbre, Eidsheim's thesis (p33) summarizes current findings:
"Contemporary vocal scientists agree there are no morphological differences that indicate race. Therefore, there should be no timbral differences based on race. However, as my opening example illustrated, and as we will see in greater detail later in this
chapter, people do hear racially-based timbral differences. I argue that such differences are based on the flexibility and possibility of the instrument, and the choices made as to which aspects of an individual vocal timbre to bring forward. Thus expressive limitations are the results of choice of use rather than of physical premises."