First of all, what is ethnic music? What makes one ethnic music different from another? For instance, what is difference between "Okinawan music" and "Scottish music"? My opinion is that melody (scale), chord, rhythm, and instruments make each music different from one another. Take, for example, melody. As a plain example, let us compare rock with blues (they are not ethnic music). Diatonic scale is used in rock. Scale that includes blue notes is used in blues. As for chord, let us compare rock with jazz. Simple chord (triad) is used in rock. Chord that includes 7th is overused in jazz. The chord progression of jazz is more complicated than rock. As for rhythm, 8 beat is often used in rock, 16 beat is often used in fusion and shuffle (triplet) is often used in jazz. Finally, as for instruments, let us compare the instruments that are used in classic with rock. The difference is quite obvious, isn' it? When it comes to ethnic music, every region has its own original instuments. So, I think instruments are one of the major factors that characterize each ethnic music.