The following is from a 1995 exchange between author and music journalist Jon Savage and Deep Soul/Northern Soul impresario Dave Godin:
J.S. Why do people become purist about this [black, soul] music?
D.G. Maybe it[']s aesthetic. I find that when you get into a passion about anything, you get into a refining process. If you were paid to see every film… if you’re exposed to a lot of something, your taste becomes refined. You become conscious of what you prefer, and with soul music, it is so much more than just music. It is also part of black American history. It’s as if some cultural thing had been developed in Grimsby, which totally reflected Grimsby, and lived and thrived in Grimsby for two hundred years before it began to seep out, there would always be a Grimsby authenticity, we would always be able to tell what was just pretend.
An Australian in Alice Springs once told me that Aboriginal painters were becoming wise to the fact that visiting art buyers had absorbed the basics of native Australian culture, and often wanted to know the story, or "dreaming" behind an otherwise purely aesthetic dot painting. It was suggested that, to meet this demand, stories were being mashed up, or just invented. This was partly to encourage sales, but also to conceal from the touristic mind the deeper content of native Australian culture.
Let's say that some of the men and women whose songs were recorded by the great folk song collectors were also giving performances, perhaps tempered for the visitor who was going to record their song. I wonder how the collector, dropping in for a day with notepad or tape recorder, was able to distinguish what today's folk aficionados would like to call "authentic" from that which was deliberately nuanced for the visitor's attention.
I was once a guest in the house of an Irish fiddle player before, during and after the visit of a German fiddler who came to learn some tunes. I can't make a detailed judgement of the music transmitted from musician to musician, but I remember that personas and behaviours were subtly altered during the visit, and that some quite humorous things were said in the house afterwards.
Typically, the process of distinguishing what's authentic from what's not involves setting limits which reflect the rule of an interested group. Dave Godin uses his 'Grimsby' example - in which only the insider can make fully-informed judgements - to illustrate the importance of insider status within musical tribes. A made-for-sale Aboriginal painting can be the authentic work of a painter's mind, hand and eye, without necessarily being an authentic part of what the buyer wants to think of as Aboriginal culture. A fiddler might demonstrate some tunes for a visitor, but reveal little of the life he leads - a life nevertheless said by the aficionado, later, to be intimately linked to the authenticity of the music. If, twenty-five years on, I learn the tunes from the German visitor, will I be acquiring authentic Irish folk music?
Authenticity is questionable even at the founding level of an artistic category. It can't be objectively established, because the preferences and arguments of an authenticating group can be as influential as the defining forms. The category of folk music may depend on the existence of long-established musical and narrative forms, but it's maintained by various individuals and groups, many of whom will set different criteria of inclusion. There can be forms and fans and arguments, but authenticity can't be settled.
 Many know of Cecil Sharp (re. U.K.) and Alan Lomax (re. U.S.), but there are many more. Try http://en.wikipedia.org/wiki/Category:Folk-song_collectors_by_nationality