Your question, "Why slight photography?" is well-taken. The truth is that I had written a section on photography, but found it impossible to match it with another Modernist venture (the way dance was to music, or design to architecture), and so, reluctantly, I dropped it. I certainly agree with you that the clear reference to photography on the lively jacket of my book only arouses the wish to read about Man Ray (whom I do mention) and photography (which I omit). To be sure, I never saw the jacket in advance, and so could not try to change it. This also meant that when the designer used her scarce space to give two of the seven possible vignettes to Picasso, I had no opportunity to comment on that choice. The jacket is, in my judgment, a success, but these details were beyond my power.
I agree that a more substantial treatment of photography (like one of opera) would have enriched the text. My only "defense" for omitting photography is that I was struck by how quickly photographers produced true masterpieces. By the 1850s and 1860s, photographers were making real works of art, with Maxime Du Camp, Gustave Flaubert's companion in his trip to the Near East, brilliantly immortalizing the great sights of Egypt, or Julia Margaret Cameron taking memorable portraits of the prominent Englishmen whose acquaintance she enjoyed. I mention them, and Mathew B. Brady, the clear-eyed recorder of the cruel realities of the American Civil War. But to discuss these masterpieces in depth would have been a highly technical enterprise. I wouldn't have been able to compare, say, a Julia Cameron with the kind of family photo that we now take without thinking twice. Even though technically the two are quite different, the difference would have been almost impossible for me to clarify. With movies, it is not that way. The technical achievements are palpable and identifiable. Orson Welles can present sights in distinctive ways that most of his precursors could not: See Chaplin.
Your disagreement with me on the "aristocratic" nature of Modernist art sounds at first reasonable enough. It is certainly true that a number of Modernists did play with "common" or "popular" themes. But it is interesting that when you talk about that, Mia, you draw your evidence largely from movies. Poets, novelists, playwrights, architects, and other Modernists were often difficult, self-consciously so (the poets especially). You note that Picasso and Braque used newspaper clippings in their canvases, but you cannot believe that they trusted "ordinary" people to enjoy their Cubist inventions.
By and large, Modernists presupposed a cultivated audience. And difficulty meant "high" art against "low" art. Marcel Duchamp's more or less deliberate attempt to destroy art as such with his readymades, for example, shows that Modernist artists knew perfectly well that their audience would probably be limited. Duchamp, it seems to me, was contemptuous of, or indifferent to, "ordinary" viewers, whether in museums or at art dealers. He took above-average risks, and essentially looked for the elite audience to understand them. Artists like Duchamp split the public into three rankings: the vulgar masses (no real interest in art); the well-to-do middle-class (smaller than the vulgarians but still sizable, and not really, truly in love with art); and the elite (which comprehends the difficult art that avant-gardes present to the world without apologies or explanations).
But by the time of Pop art (the 1960s), these distinctions had become quite unclear, if not invisible. By largely erasing the gulf between high and low art, by democratizing their art, Modernists eventually gave up what most distinguished them: the barriers that separated them from the mob. I suppose that we are still too close to the '60s to see what really happened there. But in general, I find my concerns about that period as a possible end to Modernism, though not assured at all, fairly probable. That said, I do not feel dogmatic about the "end of art." You may note that I put a question mark after the title of my last chapter, "Life After Death?" because as a historian I do not find predictions my specialty and I do not know if Modernism can survive. If it can in this democratic age, all the better. In any event, this question mark was deliberate and the result of some thinking on my part. If I am wrong, as I said, I will be delighted. Bilbao was a thrilling experience for me precisely for that reason.