Performances of the United States' national anthem are a pre-game staple at sporting events across the nation.

Because the National Hockey League has five member teams in Canadian cities, fans at many games hear the both the American and Canadian national anthems — "The Star-Spangled Banner" and "O Canada."

But at Sunday night's playoff game between the Anaheim Ducks and Edmonton Oilers in Edmonton, Alberta, Canada, something went awry during pre-game ceremonies. When Canadian country recording artist Brett Kissel walked onto the ice to sing the "The Star-Spangled Banner," his microphone cut in and out — before failing altogether.

That's when the home crowd, filled with loyal Edmonton Oilers fans, began singing the American national anthem together — all 18,000 of them.

An incredible moment

When the mic doesn’t work, the crowd takes over & belts out The Star-Spangled Banner...

...In Edmonton

🇺🇸🇨🇦 #StanleyCup pic.twitter.com/pWvrlknbV6

— NHL (@NHL) April 30, 2017

"An incredible moment," the NHL tweeted following the incident. "When the mic doesn’t work, the crowd takes over & belts out The Star-Spangled Banner...In Edmonton."

Kissel confirmed on Twitter after the incident that, indeed, his microphone wasn't working:

According to OilersNation.com, the incident was not pre-planned and the loyal Canadian fans were able to sing the anthem in unison from start to finish without any words being placed on the screen.

The Ducks went on to win Sunday's game 6-3, but the Oilers lead the series 2-1.