Fischer’s opera “The Red Heifer” is a biting satire about Hungarian anti-Semitism. Illustration by Annette Marnet

On an icy January night in Budapest, with the temperature descending through the teens, a group of young people huddled outside the Millenáris Teátrum, a performance space on the west side of the Danube. They were waiting to see a midnight concert by the Budapest Festival Orchestra, a thirty-year-old ensemble that has gained international renown not only for its grainy, potent music-making but also for its disruptive approach to the business of putting on concerts. Many curious things have happened at B.F.O. events. The arrangement of the orchestra often changes, with flutes showing up amid the violins, and vice versa. The program is not always announced in advance. On certain nights, the music is picked by an audience member, the chooser determined by a slip of paper drawn from a tuba. Players may start tangoing during Stravinsky’s “Tango”; a live tree may appear onstage during Beethoven’s “Pastorale” Symphony. The B.F.O.’s Midnight Music concerts, aimed at a youthful crowd, are full-on happenings, intended to strip away routine while leaving the music vibrantly intact.

The instigator of this methodical madness is the conductor, composer, opera director, and political gadfly Iván Fischer, who co-founded the B.F.O. in 1983. When I entered the Teátrum, Fischer was pacing around the space, making final preparations. The setup was like nothing I had ever seen. Arrayed among the players’ music stands were dozens of beanbag chairs and foam seats, on which listeners would be invited to sit. (Alternatively, they could sit on bleachers, which had been set up along one side of the space.) The idea was to break down the barrier between orchestra and audience, placing the public in the thick of the action. Fischer was pulling the beanbags this way and that, his face preoccupied, as if he were playing a surreal form of chess.

“Perhaps you should sit here,” he said to me, indicating a beanbag just behind the seats for two lead cellists. He speaks English with lyrical ease, his lightly accented voice skating up and down in pitch and lingering over words that he enjoys. “But, really, you can sit anywhere. You can lie under the piano, if you so want.” I followed his original suggestion. “Very good!” he exclaimed, his eyebrows leaping upward. “You will be embedded with the cellos.”

Fischer is a youthful sixty-three. Of medium height and barrel-chested, he is quick and alert in his movements; like many conductors, he communicates a great deal with his eyes, which dart and glitter. His hairline receded when he was fairly young, and, like many men who go bald early, he seems to age barely at all. Watching him, you sense a contradiction: he is a meticulous musician, dissecting scores with Old World rigor, yet he also has an anarchic disdain for decorum. Last summer, when he led his own production of “The Marriage of Figaro” at the Mostly Mozart Festival, he sat in front of the orchestra before the performance began and struck up a conversation with audience members in the front row.

This subversive streak goes hand in hand with an uncommon political outspokenness. At a time when illustrious conductors have aligned themselves with powerful regimes—Valery Gergiev is a prominent supporter of Vladimir Putin, and Gustavo Dudamel has failed to distance himself from Nicolás Maduro, Venezuela’s President—Fischer is a vocal opponent of Fidesz, the Hungarian right-wing party that has been edging toward authoritarianism since it won a supermajority, in 2010. Fischer recently composed “The Red Heifer,” a bitingly satirical opera on the subject of Hungarian anti-Semitism, which has seen a resurgence in recent years.

The players began filing in with their instruments. Most are Hungarian, but a fair number are foreign-born. Unusually for an ensemble of international reputation, the B.F.O. has a freelance membership. Although the musicians lack the security of a union job, they have more independence and assert themselves accordingly. I noticed that some of them meddled with Fischer’s scheme, nudging the beanbags away with their feet. The cellists with whom I was embedded were Kousay Mahdi, a native of Iraq, who came to study music in Hungary in 1985, when he was in his late teens; and Antoaneta Emanuilova, a thirty-four-year-old Bulgarian who grew up in Germany and studied at Juilliard. “Are you O.K.?” Emanuilova asked me as I sank into the beanbag. Hearing that I was from New York, she described a favorite jerk-chicken place off Eastern Parkway, in Brooklyn, where she lived when she was at Juilliard.

The program consisted of two works: Prokofiev’s Third Piano Concerto, with the Georgian-born, Indiana-based virtuoso Alexander Toradze as the soloist, and the “Polovtsian Dances,” from Borodin’s “Prince Igor,” with chorus. At the front of the stage, Toradze, an amiable bear of a man, was warming up at the piano, trying out jazzy chords. Fischer began making scat-singing noises into a microphone. He also gave instructions to the choral singers, who were to be seated in the audience. They were from the Czech Republic, and Fischer addressed them in German, which in Central Europe rivals English as a lingua franca. “Nicht zusammen!” he called out. “Not together!” By this he meant that the singers should spread out in the Teátrum.

Soon audience members, many of them in their teens and twenties, were sitting on the beanbags and in the bleachers. Around midnight, Fischer picked up his microphone and introduced the concert. “Tell us what is important about Prokofiev,” he said to Toradze, in English. Toradze answered, “It is a very cosmopolitan piece. It has themes from all around the world.” He highlighted the fact that the main theme of the second movement had a Jewish contour. I later asked Toradze whether he had intended any political message in the choice of the word “cosmopolitan”; he said that he hadn’t. But it is worth noting that right-wing extremists in Hungary, who have made their presence felt in recent elections, have often attacked pan-European and cosmopolitan tendencies, sometimes with the implication that Jews, Romanies, and homosexuals, among other groups, lack true devotion to Hungary.

Acoustically, the Prokofiev left much to be desired: those of us on the beanbags had a hard time hearing the piano, while those seated at the front of the bleachers may have heard little else. Yet it was revelatory to listen from such a peculiar vantage: you could grasp how the cello parts fit into the whole, as simple figures contributed to a machinelike mass. And you could watch a major conductor as players saw him: cajoling, marking time, looking faintly annoyed at a balance issue, smiling at Prokofiev’s quirkier touches, throwing himself viscerally into the fortissimos.

Fischer then introduced “Polovtsian Dances” with a discursive, ironic summary of the plot of “Prince Igor”; he kept laboriously over-pronouncing the name of the hero, Igor Svyatoslavich. This performance had a magical effect. Unlike most of the audience, I knew of the surprise in store—the Czechs began singing from their positions amid the audience, and eventually rose to their feet and swayed about—yet the sensation of the sound, woven around the ears, was still a pleasurable shock. The crowd was rapt; even though the concert ended at 1 A.M., dozens stayed to chat about what they’d heard.