The job of a publisher is to identify and cultivate talent, underwrite the writing process, and distribute the result. The publishing industry has been wringing its hands about the future of the print book for some time, but that model is sound (in the abstract) regardless of whether a book is printed on paper or transmitted over the Internet to a paying reader.
But what if you’re a publisher of works that have been in the public domain for a long time? The talent has already been identified and the writing has already been done, so the only value to be added is in editing, printing and distributing. That pretty much describes the business of publishing classical music scores, and the amount of value that publishers add varies greatly — between Dover, which mostly produces cheaply-bound facsimiles of out-of-copyright editions, and the German publishers Barenreiter and Henle, which produce beautifully printed scholarly editions.
Regardless of quality, all of these publishers face disruption in the form of the International Music Score Library Project, which makes 67,927 works of public-domain classical music available, for free, as scanned scores from academic music libraries. Traditional publishers rely on sales of warhorses like Beethoven’s piano sonatas to fund their operations, and that’s precisely what’s most readily available at IMSLP. It’s as though Knopf needed to sell Great Expectations to supply Robert Caro’s typewriter ribbon.