Public acceptance of an interpretive stance involves a variety of credibility issues, not only due to the basic critical component of an audience, but due to the inherent nature of musical knowledge, both for better and for worse. When it comes to a desire for "authenticity" in medieval performance, there are many details we will never know. While they are mere details in some sense, items such as absolute pitch & timbre have a direct and immediate effect on the sounds actually produced. Moreover, we cannot exactly recapture the music's original context, no matter what we do, simply due to the passage of time and our own changing relationships. In some ways, such as the modern concert setting (or recordings), we do not generally want to be historically accurate, even to the extent we can be. One might not want to be historically accurate in other ways either, and so an interpreter can adopt a distinctly ahistorical stance. Such a stance can be successful too, if it is stated explicitly and coherently. In the current era, however, audiences tend not to accept explicitly ahistorical stances, even if they are well-grounded intellectually. The record-buying public is very conservative indeed, and would probably reject a (hypothetical) truly historical performance flatly. It would sound too different from what they know and enjoy. In fact, despite its nominal insistence on historical fidelity, the public is often unwilling to let go of its previous impressions, even when they are factually inaccurate. The persistence of such fallacies is tied to various factors.
Why would otherwise intelligent people cling to disproven notions regarding music history? That is the question, and one which can often frustrate attempts to communicate. One fundamental reason concerns the many open questions in music history: For performances an audience may have heard in the past, certain choices — or guesses — regarding certain aspects of the music had to be made. There is no way to abdicate such choices and still make a sound. However, in some cases, performers today no longer need to guess, or rather they might have a narrower range of possibilities from which to choose. Nonetheless, the conservative public has already accepted and internalized the earlier choice, and may be intellectually incapable of revisiting it. While scholars in the field are pleased to have learned something new, the public's increasingly hostile reaction leads to mutual bad feelings. That said, there is something to be said for having more possibilities from which to choose, i.e. either being ignorant or choosing to be deliberately ahistorical. While the latter is actually an easy escape from such a conundrum, it is also mostly taboo. The public insists on some form of authenticity, but new knowledge is only slowly accepted, if at all. When this music was first resurrected, the public was open to its possibilities, but now many believe they know how it should sound. It has created its own new tradition, and it is an increasingly conservative tradition. Moreover, many adults were able to study it in school, and so their sense of authority forbids acceptance of new ideas. They still have their old textbooks, to which they will turn, and this is true even of generalists among music professors. Quite simply, what they learned first made the strongest impression.
That fallacies can persist with the textbooks which contain them or the people who learned them is hardly surprising, nor is the general notion that people might prefer ahistorical interpretations. Indeed, if old music is inherently good, why not old historical explanations and old interpretations? The classical mainstream, such as it is, already tends to prefer old recordings of Beethoven et al. to new ones, and such a record collectors' mentality is extended directly to the niche market for early music. People are emotionally wedded to the idea that these older interpretations have not become ahistorical (or even wrong-headed), although they do not generally let such a suggestion bother them with respect to HIP performances of later music. More than that, the rush to re-canonize early music has made programs as resistant to change as interpretations. I have already lamented the way that works are repeated on recording at the expense of variety, having been institutionalized based on arbitrary choices by the first interpreters. This sort of conservatism (essentially a fallacy of stature) is more difficult to explain, but is perhaps based on an over-abundance of good music which could be brought before the public. It arises from similar political forces to those conditioning academic pettiness, and may relate to who "discovered" which piece. The ubiquity of bland interpretations follows a similar profile, as the joy of discovery turns into an enforced orthodoxy. In a neat cycle, the resulting repetitiveness gives the public even more reason to cling to the first interpretations, the ones which were fresh & exciting.
So I claim that the persistence of historical fallacies is tied to specialists' own reluctance to truly embrace newness. Having an opinion is an art, but getting one's facts straight is a necessary prerequisite for having a valid opinion, meaning that persistent fallacies are one reason the field of music criticism is currently so banal. Oh, there have been some reevaluations, but surprisingly few, and most which occurred (e.g. Hildegard) were based more on politics than musical reality. There are many open questions, and a continued need for experimentation, but somehow relativism itself has contributed to an enforced conservatism. The conservatism of historical musical investigation, following closely on the heels of a period of expansion, is evocative of the "null position" of scientific inquiry. Whereas "skeptics" and other hypocrites want to insist that null positions are based on some underlying simplest case, who gets to define simplicity and the so-called null position? That power is critical to the direction of inquiry, and in the case of medieval music, such positions were framed incidentally by the first interpreters. The scientific priority of falsifiability has entered art music, but based on the "accidental" null position of first hearing. Such a skewed framework is typical of today's predominant skeptical atheism, especially in a world which moves quickly to enforce any status quo.
Professed skepticism tends to be a justification for deeply held beliefs, and is nearly synonymous with feeling jaded toward artistic experimentation. After all, as stimulation overwhelms us, we may find what we already know to be that much more valuable — or at least secure. In effect, institutionalized skepticism encourages what it claims to prevent, namely persistent fallacies, and as that spirit enters the arts, the nature of authority & credibility become even more highly charged. Postmodernism has already brought increased public skepticism toward further academic inquiry, not least of which in music. As a group, classical music enthusiasts are also more likely to value what they hear first over what they hear last, almost by definition. Their sense of relevance is easily tied to their conservatism, yet it is an artificial relevance based on fallacies which divests art from its creativity. Simply put, historical accuracy is not artistic relevance, nor is it something to be resisted. In fact, it is a simplistic goal, if anything, yet somehow one for which the trappings of a "skeptical" worldview have provided both an imperative and an obstacle.