Sure the "native" players were drawing on certain "background" things; but then you were bringing something to the performance that they couldn't, no? A point of view that did NOT depend on stuff that wasn't in the tune. The whole "non-ethnics can't do it 'authentically' " notion is a little weak, IMO. It's viewing a piece of music as having characteristics that are not really part of the music itself. Suppose you simply heard a piece of music, knowing nothing about its provenance? Could you legitimately attempt it? Suppose you did learn it, and well, and played/sang it a great deal, and it was popular; and then someone came along and pointed out to you that the piece "really" belonged to the Makkawak tribe of Lower Slobbovia, and they did it thus and such a way, and it was sacrilege to perform the piece other than on the feast day of the Sacred Carp? Is that a quandary?