The euphoric roars as fans leaped from their Old Trafford seats took Ole Gunnar Solskjær back to the Alex Ferguson era.
Back to when Manchester United's supremacy over its neighbor was undisputed.
Back to when Solskjær was playing under the managerial great rather than being the latest coach trying to recapture those glory days.
"I was probably more used to it back then," the 47-year-old Norwegian said.
It's been 15 challenging months at the helm, from the early highs to growing dissent.
All the gloom seemed to wash away in Sunday's Manchester downpour as Anthony Martial and Scott McTominay profited from Ederson's goalkeeping errors to claim a 2-0 win over City.
The ball rolling into an empty net with almost the last touch of the game from McTominay had fans punching the air in delight, and cheering across the stadium,
For the first time in a decade, United had completed the double over its neighbor, by beating City home and away in the Premier League.
Ferguson, still in the dugout the last time that happened, was beaming in the directors' box this time.
"The desire and work rate, that's what I think the fans love about these players," Solskjær said. "To see the connections between the players, the team and the fans today. What an atmosphere. At the end, seeing everyone in the stands. You turn around and you see Sir Alex up there, he is proud and it's a big moment for every one of us."
But this is only one step on a longer journey back to turning United into Premier League champions for the first time since Ferguson's retirement in 2013.
Victory over City only took United into fifth place, three points behind Chelsea, which beat Everton 4-0 in Sunday's other game thanks to goals from Mason Mount, Pedro, Willian and Olivier Giroud.
But City is 12 points in front of United in second place but now closer to surrendering the title to Liverpool. With a 25-point lead, Liverpool only needs two more victories from nine games to end its 30-year title drought.
City has now lost seven games in its title defense — the most in a season since 2015-16 when it was defeated 10 times before Pep Guardiola arrived.
Culpability on Sunday was with Ederson.
The goalkeeper allowed Martial's shot to squirm under him on the half-hour when the City defense was caught out by Bruno Fernandes chipping in a free kick.
The second blunder came in second-half stoppage time, rolling the ball straight to McTominay and the midfielder struck from distance into an empty net.
"We conceded a goal and we should avoid it," Guardiola said. "We knew Fernandes sometimes is chipping the ball.
"He's an exceptional goalkeeper. I'm not here to judge my players. He will recover and he is a special talent."
Defending his players who have won back-to-back titles, Guardiola was tetchy. They're back in action on Wednesday at home to Arsenal.
"We played really well," Guardiola insisted. "It's not lack of motivation or lack of concentration. So it happens, mistakes are part of the game. The good actions are part of the game. But the behavior is good and how quickly we moved the ball, how we arrived in the final third, especially in the second half in the good position. So I'm satisfied for the way they played."
But it was United who went a 10th game unbeaten in all competitions, a run that includes eight clean sheets.
"They've learned through some hard times in this season," Solskjaer said, "because we have been a young team and we have started something that we believe in."
That has been helped considerably by the January arrival of Portugal midfielder Fernandes energizing the club.
"He's got the desire and commitment," Solskjaer said. "He's a risk taker. He's got courage. He's brave enough to make mistakes. And if you make enough mistakes, they'll be corrected into fantastic assists or goals."