In the summer of 1830, King William I of the Netherlands scheduled a multi-day birthday bash in Brussels, and he expected everybody in the city to join in the fun. The celebration, however, would not go as planned: Political turmoil, which had been brewing in the city for months, would cause two public events—a fireworks display and a procession—to be canceled. One of the few public events to remain on the schedule would be an August 25 performance of the opera The Mute Girl of Portici, by the French composer Daniel Auber.

Like the other events planned that week, the show would experience a few hiccups.

In the mid 1830s, tensions in the United Kingdom of the Netherlands were at a boil. In the north, most citizens (King William I among them) were Dutch Protestants. In the south, most people were French-speaking Roman Catholics—and they were demanding independence.

Considering this growing atmosphere of discontent, King William I's choice of opera was a questionable one. The plot of Portici's fiery libretto revolves around the Neapolitan revolts of 1647, telling the tale of Masaniello, the real-life Italian fisherman who led an uprising against the rulers of Naples. (The opera itself was revolutionary, too: Among the first of its kind in the genre, this "French grand opera"—called La Muette de Portici in its native language—was a lavish and large-scale spectacle that, most notably, had integrated ballet and mime into the performance.)

One could say the opera's place in history was preordained: It was one of the final public events for King William I's celebration and, after the cancellation of the fireworks and the procession, one of the few events locals could openly protest. Days before the show, the newspaper Courrier des Pays-Bas suggested that concertgoers should leave the performance at the fifth act. Many of the attendees, however, were so moved by the opera's nationalistic music that they left much earlier. During a second act duet, called Amour Sacré de la Patrie—or "Sacred Love of the Fatherland"—the crowd began to cheer so wildly that the performers reportedly had to stop singing and start over.

Eventually, the performers reached the peak of the piece's lyrics—singing Aux Armes, that is: "Call to Arms"—and dozens of spectators stood from their seats and ran to the streets. When the fifth act arrived, audience members began to loudly boo in an attempt to stop the show and incite a riot. "The delirious crowd [hurled itself] out of the hall—and into history," wrote 20th-century French composer Lionel Renieu. "Welcomed by the other crowd which waited outside, it joined in the demonstrations which loosed the revolution of 1830."

Indeed, the musical performance had invigorated the crowd. The audience passionately chanted patriotic slogans, stormed into government buildings, and began destroying factory machinery. Within days, they were flying the flag of Independent Belgium, which was tied to a standard with shoelaces.

The dissent in Brussels was powerful enough to attract the attention of other disaffected working class people in the south, and soon thousands more would join the cause. According to the History Channel, just one month later, "the city fell into bloody street battles between the military and the rebels, who were eventually victorious. They drafted a Declaration of Independence on 4 October, and on 20 December the London Conference declared the United Kingdom of the Netherlands was dissolved." Soon, Belgium was its own independent country.

Years later, in 1871, the German composer Richard Wagner—who had met the elder Auber numerous times and had conducted a production of Portici himself—wrote in his book Reminiscences of Auber, "[S]eldom has an artistic product stood in closer connection to a world event."