Here a degree thesis (in italian language) by Massimiliano Buldrini, italian overtone singer, actor and experimental music/sounds lover. The subtitle, Similarity and contaminations between East and West, give us the idea about his work. From vocal acoustics and hearing to eastern and western styles (America, Africa, Sardinia and Tibet, Mongolia, Tuva).
At the end some interesting interviews.
In my opinion, a simple but very clear discussion dedicated to beginners and neophytes.
Buldrini_Massimiliano_Tesi2009 Unlinked for some time.