And therein lies the seed of Rubinstein’s, and his opera’s, excision from music history: He did not think “Demon” was obliged to sound Russian.

“His melodic and harmonic practices were from a Western point of view,” Mr. Botstein said. “He didn’t particularly believe in folk melody or folk rhythm as an inspiration. Rubinstein would have been more attracted to an international language of culture and audience that wasn’t simply an instrument of national assertion.”

But the generation of Russian composers that followed him, particularly the group known as the Five, or Mighty Handful (including Rimsky-Korsakov as well as Mussorgsky and Borodin), favored aggressively nationalistic music, grounded in folk inspiration. What to Rubinstein had been the professionalization of composition was for this group unwelcome Westernization.

They and their propagandist, the critic Vladimir Stasov, condemned Rubinstein in print. César Cui, another member of the Five (along with Mily Balakirev), would credit Rimsky-Korsakov with the first Russian symphony, even though Rubinstein had completed his first more than a decade earlier. Unlike his younger competitors, Rubinstein “didn’t sport an eastward-looking definition of the Russian sensibility,” Mr. Botstein said. “He was a patriot, but he was not an ethnic nationalist.”

That national flavor is what the Five, who were all self-taught, wanted, and to some extent we still approach Russian music on their terms. Germans and other Western Europeans are often said to write music that’s generic — in the best way — and universally accessible, while we evaluate Russian music based on its Russianness; it is inextricably marked by its creators’ nationality. (In the 20th century, Stravinsky spent decades trying to shed the label of “Russian composer.”) Rubinstein therefore doesn’t fit into the way we often discuss his country’s repertory.