*I'm unconvinced that an Italian Futurist rave counts as "classical," but, when it was first premiered none of it was "classical," it was just music.
https://en.m.wikipedia.org/wiki/List_of_classical_music_concerts_with_an_unruly_audience_response
There have been many notable instances of unruly behaviour at classical music concerts, often at the premiere of a new work or production:
1802 (December 18, London): William Reeve, Family Quarrels. Part of the Jewish audience catcalled because of perceived anti-Jewish slights.[1]
1830 (August 25, Brussels): Daniel Auber, La muette de Portici. Audience members at a performance in Brussels left before the end of the opera to join pre-planned riots that were already taking place across the city, marking the beginning of the Belgian Revolution.[2]
1838 (September 10, Paris): Hector Berlioz, Benvenuto Cellini. The audience hissed at most of the music after the first few numbers.[3]
1868 (March 5, Milan): Arrigo Boito, Mefistofele. The audience came predisposed to drown out Boito's claquers and succeeded in making the music inaudible with their hisses and boos.[4][5][6]
1913 (March 9, Rome): Francesco Balilla Pratella, Musica Futurista. At the second performance of the work, the audience booed, threw garbage at the orchestra, and some fighting occurred.[7][8]
1913 (March 31, Vienna): Alban Berg, Altenberg Lieder. As part of a front in Vienna's ongoing style wars, the audience booed and catcalled loudly, and some punches were thrown. The event came to be known as the Skandalkonzert.[9]
1913 (May 29, Paris): Igor Stravinsky, The Rite of Spring. Dueling factions tried to drown each other out during the ballet's premiere, unwittingly launching generations of exaggerations of what actually happened in the hall that night.[10][11]
1913 (September 5, Pavlovsk): Sergei Prokofiev, Piano Concerto No. 2. The work was met with hisses and catcalls.[12]
1914 (April 21, Milan): Luigi Russolo, three works for Intonarumori (The Awakening of a City, The Meeting of Automobiles and Aeroplanes and Dining on the Hotel Terrace). A concert organized by the Futurists to provide the first public demonstration of their experimental "noise-making" instruments called intonarumori resulted in an expected fracas,[13] with Futurists led by Filippo Tommaso Marinetti fighting members of the audience in the stalls.[14]
1917 (May 18, Paris): Erik Satie, Parade. One faction of the audience booed, hissed, and was generally unruly, but they were eventually silenced by an enthusiastic ovation.[15][16]
1923 (March 4, New York): Edgard Varèse, Hyperprism. The audience laughed throughout and hissed at the conclusion, which prompted Varèse to repeat the work in hopes of a more serious response.[17]
1924 (June 15, Paris): Erik Satie, Mercure. The police were called to the premiere due to unruly behavior that sprung from the Parisian cultural infighting of the time.[18]
1926 (June 19, Paris): George Antheil, Ballet Mécanique. The premiere performance received a large ovation despite some unruly behavior in the audience, including an outburst by Ezra Pound, but there were some fistfights in the street after the concert.[19]...
