The Globe and Mail wrote an article over the weekend about a bench-clearing brawl between the Philadelphia Flyers and Montreal Canadiens that took place before their playoff game even began way back on May 14, 1987. It is titled "The fight that changed hockey."
The brawl all started, apparently, because Claude Lemieux had this pregame ritual of shooting pucks into the opposing team's empty net to end warm ups and the Flyers had warned him not to do it. Being Claude Lemieux, he didn't listen and things escalated rather quickly. Add on the fact that there wasn't a referee in sight and these guys were going at it forever. [video below]
I'm almost positive the organist plays "Final Countdown" at one point.
I think this sums it up:
[Chris] Nilan recalled fighting [Dave] Brown for eight to 10 minutes then having to play the game. “I was basically spent before it even began. And there was Dave sitting on the bench the whole game,” he said. “Looking back at it, it was kind of stupid.”
The whole article is worth a read to hear players talk about how that night changed the way fighting and bench-clearing brawls were dealt with moving forward.