Mistakes and Disputed Points in Music, by Louis C. Elson, was published in 1910. I've written before about my liking for old music books, and this is another fascinating find. It's not a long book, but Elson manages to cover a large amount of territory, from acoustics, through orchestration, conducting, teaching, notation, tempo and rhythm, language and pronunciation, history, form, and several other matters, including a discussion of musical mistakes in literary works of various kinds.
The main thrill with a book like this is realizing that it came out in the same year Samuel Barber was born. Charles Ives was living in New York, selling life insurance, playing the organ, and writing his Fourth Symphony (among other things). Mahler was conducting in New York; 1910 was the year his Eighth Symphony premiered in Munich, and he died after returning to Europe the following year. Amy Beach was at the height of her powers, soon to embark on a three-year European tour. Arnold Schoenberg wrote Harmonielehre that year. I doubt this book was on the bookshelves of any of them, but it certainly might have been bought by people who heard them.
Another source of interest is comparing the recommendations to more modern practice. Some of the advice is still good. Elson recommends using an up-to-date orchestration text, which is wise, though of course "up-to-date" for him meant Strauss's expansion of Berlioz. He also suggests that composers mark accidentals if there's any possibility of a question, regardless of whether it would technically be required; still a good idea. But piano pedal markings have changed considerably since those days, and understanding of 18th-century signs for ornaments has undergone revision.
Elson talks about the supposed emotional characteristics of various keys, pointing out that, since the standard pitch has risen, the keys whose characteristics Berlioz listed wouldn't be the same in Elson's day, when the standard pitch was 435 Hz. The argument has become even stronger since that time, as the standard pitch has risen still further. But Elson doesn't seem aware of the Doctrine of the Affections that preceded Berlioz, though he does quote a 1724 music dictionary (which he doesn't name) regarding tempo markings.
But there's much more here than musical technicalities. There's an anecdote about a test made with three cornets, one of silver, one of brass, and one of papier mache, which showed that it wasn't possible for a blindfolded listener to tell, from the sound, what material the cornet being played was made from. Elson puts an end to the myth that composers are generally short-lived, though he only mentions one composer who lived into his 80's (Verdi). He deals at some length with a novel, "La Vieillesse de Guillaume Du Fay", which appeared in a Paris magazine as early as 1837, and purports to tell the story of the discovery of counterpoint. The author plays fast and loose with history, but the story sounds interesting anyhow.
I'd never heard of Ouida before I read Elson's book; now I've read about the musical mistakes in some of her novels. You didn't know that Palestrina wrote "airs", or that Mendelssohn wrote masses? In her books, apparently, they did. Another author has a character play a Sonata in A-sharp major by Mozart.
This is a section that would be fascinating to update, though it might have to become an encyclopedia. Thinking only of fantasy and SF novels I'm familiar with that deal with music brings up a long list; if other novels that were written since 1910 were included, to say nothing of poems and short stories, I'm guessing it would be a nearly impossible job even to read them all, let alone discuss them. Elson, of course, doesn't pretend to be exhaustive; he only mentions a few of the more notable instances of literary license that had come to his attention.
Louis C. Elson was professor of Music Theory at the New England Conservatory, and wrote several other books, including a music dictionary. Right now that's all I know about him, but as this book shows, he had quite an amazing mind.