I've just watched this documentary and I'm still venting... I must get these vapors out of my system!
Why are people so credulous when it comes to classical music?
It's not limited to classical music. Why are people credulous? Well, for a great many reasons. In this case we have a confluence of several:
i) Bach's works have been analysed for hundreds of years, and little new information has emerged. That means it's hard for anyone to find anything new to say.
ii) its fits a nice contemporary narrative. Unquestionably, talented women have been repressed and marginalised throughout history, and only relatively recently have they received their deserved attention. This means that the potential rediscovery of another such women fits the scholastic zeitgeist, and so attracts the attention above its actual scholarly value. Twenty years ago we'd be asking if Bach's second marriage meant he was secretly gay. So it goes.
iii) the continued fascination with postmodernism in all facets of the arts mean that strong factual evidence is not actually a requirement, and people can be published on the basis of "analysis of penmanship" - a pseudoscience that makes phrenology look credible.
Probably the best way to debunk the silly claim that Anna Magdalena was the composer would be by applying Bayes' theorem to each of the categories of evidence. I have just read a fascinating book by a retired cosmologist who applies Bayes' theorem to argue that Shakespeare was not the author of the sonnets. If I have time I might do this with the Bach example but that's for another post. For now and very briefly, one would consider, firstly, the prior probability that Anna Magdalena was the composer (this would be low, since, for one thing, she is not known to be a composer). Then consider the conditional probability that Bach would do his best work given that he is married to Anna Magdalena. Finally consider the probability that he would do his best work given that he is not married to Anna Magdalena. Now I argue that the last two likelihood ratios are roughly equal hence the posterior probability would not be raised greatly, if at all, above the prior. Of course, I have only considered one category of purported evidence, that Bach did his best work after he married Anna Magdalena, but all the indications are that if all the categories are considered they will not greatly raise the prior if it is raised at all. QED.
It's a sad reflection on the current state of musicology that, rather than exploring important questions, like Bach's influences and influences on, his methods of composition and proper performance practice, someone spends their time on this ridiculous issue. Unlike a painting, the authenticity or otherwise doesn't affect anything of substance, and in this case it appears we can never know the truth. Would it make any difference anyway? Would we play, or listen to the works differently if we thought his wife wrote them?
I'm still waiting for someone to claim Bach was an alien hominid brought to earth by Erich von Däniken's extraterrestrial-friendly Mayans to further the Illuminati's centuries-old plan for world domination in conjunction with the Vatican, Tutankhamen, Scriabin, Leibniz, Elvis Presley and/or dolphins.
And we're back to questions of authorship, did Bach's wife write this, did the Earl of Oxford write Shakespeare's plays, does Victoria Beckham design her clothes – does it matter?
For art it only matters in financial terms, a different attribution can add a million quid on a painting, it's the same object before and after. It's why I prefer to look at the art in the Museu de Arte Antiga in Lisbon, mostly anonymous beautiful objects, the artists biography doesn't get in the way of seeing or hearing the work.
Bottom-Line: Bach tapped into extraordinary mathematical interplays in harmony that stretch the ear to its limit, even now, but all somehow made sense. However, one should not confuse the structural elegance with predictability. His greatest works are characterised by a sort of perpetual harmonic bifurcation: they could at any point unfold one way or the other or slip off another through relative major/minor devices. You never know which which way it will turn, you simply enjoy the harmonic journey Bach that pioneered, precisely because of his genius. He makes the unfamiliar seem familiar.
NB: If you wish to watch the above-mentioned documentary, it's here. Word of warning: The voice-over, in some parts, is in Portuguese. I think it's still watchable for those of you not conversant with Portuguese.