Martin J. Baron, the imperturbable admiral of fact-checking at The New Yorker, died today at the age of eighty-five. Mr. Baron, as he was invariably addressed, had a thirty-five-year tenure at the magazine, during which time he must have conversed, in his decorous and unhurried way ("In the next passage, Mr. Pollini, we would like to say . . ."), with most of the significant figures of the late twentieth century. I remember once looking through one of the two immense Rolodexes on his desk and finding cards for Aaron Copland and Leonard Bernstein. If I had written, say, that Rimsky-Korsakov was a superb orchestrator, he would call up Richard Taruskin and ask whether it would be fair to say that Rimsky-Korsakov was a superb orchestrator. (This is an exaggeration, but only a mild one.) He worked on most of my articles from the mid-1990s until his retirement, in 2010, and I owe infinitely much to his knowledge, his meticulousness, his gentleness, and his sympathy. In 1997, as the New York Times reported, he nearly missed his own sixtieth-birthday party because he was immersed in my essay on Schubert. I wrote in the acknowledgments to The Rest Is Noise: “Martin Baron is the greatest fact-checker that ever was and ever will be. (Leave on author.)" The last phrase is a long-standing New Yorker locution, indicating an item that cannot be checked by normal channels and is left to the writer's discretion. The son of a longtime St. Louis Symphony violinist, Martin had a profound love for classical music, and for Schubert above all. I offer the above in his memory.