“The King of Instruments.” That’s the sobriquet the mighty pipe organ goes by among those who love it—and a cue for sarcasm for those who can’t take the relentless pressure of the bellows that produce its majestic sound. If you’re in the “No kings!” camp, the Oratorio Society of New York’s free program Music of the French Romantic Period, which presents works by Louis Vierne, Gabriel Fauré, Charles Gounod, and Jules Massenet, is definitely not for you. Few rejoiced in the organ’s staggering sonic palette as they did. Also represented: the prodigious Lili Boulanger, born on the cusp of the 20th century, but silenced by intestinal tuberculosis at age 24. The man of the hour is Jon Runion, working the “manuals” (read: keyboards) with his hands, dancing over the pedals with his feet, and orchestrating the all-important panoply of registers (or “stops”). Prepare to swoon. Kent Tritle conducts. —Matthew Gurewitsch