Here's what was overheard from a seat just behind the two men:
Man A: "Psst. Your mother wears army boots."
Man B: "That's not what she told me in bed last night."
Man A: "Oh yeah? Is that why your sister was out so late at my place?"
Man B: "Fuck my sister!"
Man A: "Oh, I did!"
Man B: "Why, you son of a bitch . . ." (raises fists)
Man A: "Hey, chill, it's the second movement coming up."
Man B reluctantly lowers fists. "Okay. But watch it."
(Three minutes later) Man A: "Brahms should have written this andante, not sostenuto."
(Fistfight breaks out).