The fans' volume increased as Vegas Golden Knights forward Alex Tuch raced into the Colorado Avalanche zone during overtime. They let out a jubilant roar when he snapped a shot over goalie Philipp Grubauer to win the game and earn his team the No. 1 seed in the Western Conference half of the 2020 Stanley Cup playoffs.

Tuch didn't acknowledge the crowd as he celebrated because there was no crowd to acknowledge. The stands in the arena in Edmonton, Alberta, were empty, as they've been for every game of the NHL's restarted season in two Canadian hub cities. The cheering he heard in the arena -- and that fans heard as they watched the broadcast -- was synthetically created by computer software, a mixing board and a man whose task it is to make playoff hockey feel as normal as possible under the most abnormal of circumstances.

"I have that in the back of my mind the whole time I'm doing this job," said Jeff Kozak, who is in charge of synthetic crowd noise for all the games played at Rogers Place in Edmonton. "I'm trying to be fair to the game, if you know what I mean. I can't push it. I have to make it as natural as I can. It's been an interesting lesson in moderation. But there are also just times when you can feel it."

Kozak and his counterpart in Toronto, Matt Coppedge, are audio mixing veterans hired by the NHL and its broadcast partners to conduct what has become the most important symphony of the restarted season. The artificial cheering is meant to obscure the fact that the NHL is playing games in empty buildings. If not deployed properly, it could just underscore that awkwardness.

"We're not doing a typical event for fans. We're doing a made-for-television event because all of our fans are going to be watching at home," said Steve Mayer, NHL chief content officer and senior executive VP of events and entertainment. "This is going to be bizarro world. I'm so excited about it, but at the same time, I'm nervous about it."

The NHL wasn't the first league to use artificial crowd noise in games. The English Premier League tapped EA Sports' archive of video game cheering for its restarted season. Major League Baseball did the same using sound from "MLB The Show."

The FIFA experience showed proof of concept "both from a conceptual standpoint and a hardware perspective," said David Pritchett, presentation designer at EA Sports for its NHL games. "That gave us a lot of confidence that it could happen. But at the same time, the NHL game is very different from a soccer game. It's so much faster."

The NHL knew it needed sound mixers who knew the pace of hockey. That meant people such as Kozak, who worked in the industry for 31 years, mixing the audio for live hockey broadcasts on Canadian television.

"I had been aware that MLB and EPL had been doing this. When I was asked to do it, I thought, 'Wow, that is quite a challenge,'" he said. "It all makes perfect sense in my mind. The game is slowed down so much mentally to me that I'm able to pick it apart in small microbursts of time. It's the most unique thing I've ever done, really: providing live foley [work] to a game as fast as this."

The biggest step was figuring out the most efficient way to "sweeten" games with synthetic sound. But the first step was convincing the NHL that it needed sound for the restart in empty arenas.

"When it comes to the crowd ... I'll be 100 percent honest: There were some people in favor of adding a crowd and some people that weren't. But we're not trying to fool anyone into thinking that we had 17,000 fans in the stadium," Pritchett said. "Obviously, the NHL wanted to do something different. They didn't want to try to recreate, artificially, the experience that you would have had outside of the COVID era -- the 'normal hockey game.'"

As the stodgier voices in the NHL agreed to artificial crowd noise, EA Sports and the league began philosophical discussions about how to approach it.

"It was a discussion with the NHL about how it was going to be OK to push this. To not just do the bear minimum -- not having just a low drone of a crowd but looking to add things like the reaction to big saves, missed shots or the absolutely euphoric reaction to goals. We weren't sure at first, but we came to the conclusion at the same time that this was about the storytelling side of things, rather than trying to fool anyone," Pritchett said. "Once we wrapped our heads around that, we were really ready to start pushing into what this would sound like. But that took a while, to be honest."

Next was a discussion on how to tell the story. For example, would the synthetic cheering reflect that there was a designated home team and road team?

"The philosophy from very early was that it was going to be a neutral-site game," Pritchett said.

That meant no booing.

"I tend to call it 'disenchantment' as opposed to booing," Kozak said. "Once you introduce that sort of negative reaction, you've taken sides. You've lost your neutrality."

Kozak said that maintaining objectivity is one of the more challenging aspects of the job.

"Yeah, the neutrality thing. That's hard. Really the only advantage here for home teams is the last line change," he said. "When a team goes on the power play, they play the same music and video on the screen that they would have at home. So I'm trying to match that. Every team gets the same treatment from me as the home team. But I have a couple of little carts where if a guy gets tripped or there's a hook or something, there's a natural reaction. I like to sneak that in because it's a part of it. And I'll do it for both teams."

With agreement on the philosophical approach, it was time to figure out the technology.

Inside EA Sports' NHL games, crowd reactions are driven by artificial intelligence. To use reactions in a live game, the NHL needed hardware and software that could be used by a human operator in real time.

The system being used at NHL games is typically deployed for live concerts. "I liken it to performing a piece of music," Pritchett said. "It's not a technical task. It's an artistic task."

The original plan was to have multiple mixers in each city, but in the end, Kozak and Coppedge were the artists in residence for the postseason. They were given access to the new equipment a few days before the NHL's exhibition games in late July. Because he had never done this, Kozak spent close to six hours over the course of two days binging old game footage and sweetening it. He'd record it and then split the audio between the real game and what he had done synthetically to see how close he was.

"My initial reaction when you first start sweetening is that you go overboard," he said. "You try to sweeten everything. Every tug on a jersey. You have to learn to let it breathe a bit because there are commentators talking over the action."

The equipment they use is a combination of hardware and software. There's the Ableton Live 10 digital audio workstation, which is displayed on a monitor while the mixers use a Push 2 controller to activate and manipulate the sounds.

The controller is a box with buttons that are illuminated -- all the easier for a DJ to find them in the dark -- and color-coded to sounds preloaded into the software. There are usually multiple sounds for each event in a game. For example, under a teal-colored header that reads "goal -- applause," there are seven options, including "small cheer," "cheers, larger" and "cheers, biggest."

There isn't a specific sound for the anticipation of a goal, so the operator needs to combine tracks, some of which are called "loops." The recipe to replicate a crowd before a goal: Hit the "anticipation loop" to create simultaneous gasp, dial up the crowd intensity, and hit the cheers if a goal is scored.

The loops have been edited to eliminate "audio landmarks" that would have the tracks stick out in the mix when used -- like when you're watching a sitcom with a laugh track, and you hear the same synthetically added guffaw after every joke. It's a reminder of artificiality. That's what they're trying to avoid here.

Kozak is stationed in the press box in Edmonton. "I get a great view of the ice," he said. "It was the perfect spot to be put in because I could see the play develop. What I have found, though, because of being off for so many months, the speed of the game is so much quicker than on a program monitor."

He said the most difficult thing about his job is the instant decision-making that must take place.

"You try to get everything right, be as tight to the play as possible. So you have to be part The Amazing Kreskin," Kozak said in reference to the famed mentalist who made the late-night talk show rounds.

"When a guy's in the slot, one of three things are going to happen. Either he's going to miss the net, he's going to score, or he's going to get crushed by somebody. In that split second, I have to make the decision on which effect I'm going to use to accent the play," he said. "As time has gone on, my decision-making has gotten sounder. But you're never going to get it at 100 percent."

For a huge "crush," it would be an "eww." For another result ... well, Kozak has many options. "I usually end up combining sounds at the same time, because of their different inflections, to try and match their emotions. I know it sounds crazy, but EA has given us so many sound samples that we can really paint a sonic picture."

When there's a puck that's loose around the crease, Kozak has the ability to recreate all the emotions, all at once, in one chaotic moment: gasps, cheers, screams, consternation and, rising up through the cacophony, euphoria if the puck crosses the line and the referee signals a goal.

"If it's a tie game or a one-goal game in the last minute of play, I'm going to ride my intensity crowd loop much higher than I would in normal play. Because that's what the crowd would do in that situation," he said.

But the job is also about when not to sweeten the audio, such as when play is stopped because of an injury. One of the qualification round's most horrific moments was when Toronto's Jake Muzzin hit his head on an opponent's leg as he fell to the ice. The symphony of crowd noise ceased, leaving fans at home to hear nothing but the sounds of the stretcher being prepared to cart Muzzin off the ice. It was eerie but necessary, Kozak said.

"That's something we'd normally do in a broadcast," he said. "When a player goes down and is seriously injured, everything just shuts right down. It's a very serious moment. At that time, it's more about the player than anything. All the families of the players are watching the game, right? So that's the hard-and-fast rule: Let the story play out. Don't affect it in any way. It's a serious moment. You don't want to sweeten anything. It's the right call, for sure."

As the tournament rolled into the next round, there have been trials and errors. Kozak first kept his headphones on, DJ-style, before realizing that he needed to hear the sounds of the game. "I think that was the smartest thing I ever did, was to go au naturel and do the job like that," he said.

The NHL also changed things. It decided to bring the crowd noise into the arenas for players to hear. Originally the plan was not to do so, given the workflow of the rights holders and the uncertainty about how the noise would be received.

"Everyone at home had the option to hear [natural sound] or hear the audio tracks that I'm mixing in with the natural ice sounds," Kozak said. "To keep the integrity of the ice effects, it was decided not to put the synthetic audio into the building. But then we found out that everybody wanted it. At first, it was nice to hear the natural audio, but people missed the noise."

For months, they missed the noise as well as the ice, the goals and everything else that's aesthetically hockey. The artificial crowd noise isn't always perfect. Sometimes, it's like the "uncanny valley" when trying to create film characters using CGI: Just as there's always something off about the eyes, there's something inherently spontaneous and emotional missing from synthetic cheers.

But squint your eyes hard enough, and this looks like playoff hockey. Close them all the way, and it sounds like playoff hockey. That's what Kozak hopes he's helping to create.

"You're proud to actually make it work," he said. "It's overwhelming, actually, the response. I'm taken aback by the whole thing."