It truly must be playoff time in Edmonton, when Oilers fans are drawing fans of their own.
Before Sunday's second-round game against the Anaheim Ducks, when the anthem singer's microphone suddenly went south, more than 18,000 fans jammed into Rogers Place picked up the slack and belted out The Star-Spangled Banner all on their own.
Most times, players and coaches are in the zone during anthems. But this rendition of the American anthem was not lost on anyone.
"As an American, for a Canadian to sing the national anthem was pretty special to me," said bruising Oilers winger Patrick Maroon, who was born in St. Louis, Mo. "They should all be proud, and it certainly got me going. That was pretty cool."
Oilers play-by-play commentator Jack Michaels, who grew up in Pennsylvannia, noticed what was going on right away, and managed to record about 10 seconds of the crowd singing the American anthem and posted it to his Instagram and Facebook accounts.
"What was really remarkable, and to me what's lost in this, is not only the fact that they were emotionally invested in the anthem but also the intelligence, the collective intelligence of 18,000 people to pick up what was going on and what [singer] Brett [Kissel] needed, and just an impromptu rendition.
"Come on," Michaels said. "That was just phenomenal."
Americans noticed as well.
The a-cappella anthem made the news south of the border. On Fox News on Monday, an anchor noted that Oilers fans "belted every single word of our national anthem" and called the impromptu moment "a great tribute to our neighbour in the north."
For Oilers head coach Todd McLellan, who spent more than a dozen years coaching in the United States with the Detroit Red Wings and San Jose Sharks, hearing the crowd sing the anthem proved something he has known for quite a while.
"As it turns out, a glitch can produce a great moment," said McLellan, who initially thought the whole thing was supposed to happen that way.
"Speaks volumes of the quality of person that lives here in this community," McLellan said. "It would have been very easy for them to be quiet and not show the same energy and passion for the Canadian anthem. But certainly, proud to say that I'm from Edmonton today, and I think everybody around me can say that as well."
There were times during the regular season when the Rogers Place faithful were almost mouse-like (see: quiet as a ...).
But during this playoff run, the first for Oilers in 11 years, the mouse has roared.
For his part, Kissel was appreciative of the help he got Sunday.
'I didn't have a plan B'
"It was such a moment of panic for me as an entertainer," Kissel told CBC News Network host Christine Birak.
"You know, I've been through technical glitches before over the course of my career. But you go through something like this and the magnitude of playoff hockey in Edmonton, and such an important song.
"I didn't have a Plan B, so I didn't know what to do."
The fans did. A YouTube video of the anthem became an instant hit online, and has been viewed more than 60,000 times.
"It was a major technical glitch, and you can never predict these things," Kissel said. "And I'm just so proud of the fans here in oil country, as Canadians in Edmonton, to bail me out. Because it could have been one of the biggest anthem fails of all-time, and it turned out to be a magical moment."