What you propose is largely an intellectual exercise, in which one can triangulate on the songs of any given region and culture based on 1) what they do now (and determining how widespread the practice), 2) what they say they used to do, and 3) any recorded evidence (in the most general sense--whether written down ages ago or captured via some electric medium).
There is never going to be a completely "authentic" description or performance of the Ur songs of any of those cultures, but I suspect you could find some very interesting fragments that contribute to the authenticity of modern performances. Things that are idiomatic to the cultures in question that have been passed down unchanged (even though the understanding or meaning are less well understood).
Political correctness is a scourge to a lot of scholarly work. You spend so much time trying to find the blandest and least "offensive" (and offensive to whom?) description that you lose the momentum of what you're doing by the time you've included all of your hyphenated qualifiers in your report. When possible, ask the parties in question what they call themselves, stay away from the rude or derogatory terms, they don't advance scholarship anyway, but don't worry about the rest. It'll sort itself out 100 years from now in some way you can't anticipate anyway.
If you're researching music you must keep yourself open to the humanities in general. Looking only in musicology sources you will miss songs transcribed as poems, literature that includes references or fragments of songs, durable art forms that contain visual reference to songs or stories. What philosophers were active in an area centuries ago? Africa really wasn't the "dark continent" except that Europeans tended to write it off and not acknowledge the art and science as important when compared to their own. That doesn't mean it didn't exist. Euros simply didn't know or care what they were looking at. I've spent more time working with American Indian literature, so will use that to illustrate the rest of my thoughts.
Scholars from many disciplines study American Indian cultures and wonder at what came before the "contamination" (as you call it) of European culture. Where Indian groups weren't wiped out, and in fact had a chance to commingle with the Euro colonists, they at least had a chance of passing down Indian cultural material. Had the Euro entrance onto the continent been less bloody, it might have been even more disruptive to Indian cultures if they blended earlier and easily adopted the European way of things. The syncretic ability of tribal people to take something useful from new cultures and blend it with their own allows for survival and growth (and this probably isn't limited to American Indian cultures). You must realize that even had Europeans NOT conquered North America, had instead stopped at the borders to trade, the Indian songs and stories that are sung and told now would be vastly different from what they were singing and telling centuries ago. I think it would be futile to try to perfect a view of what a culture was, and what they might have been without interruption, because the result often tends to devalue what they are now, implying imperfection or flaws come with dilution. This is in no way an apology for the agonies of colonization as waves of it occurred on this continent. But it is an acknowledgement that there's no going back or undoing the cultural mingling and growth that has happened.
Enjoy the process, and revel in the discoveries as you search, but don't hold the past as more "authentic" or valuable. That gives the impression of dismissing the people and cultures who are here now.