On this occasion, the final whistle sounded like music to David Moyes' ears.
This hasn't always been the case in the Scot's tumultuous first season in charge of Manchester United.
In Athens three weeks ago, the same shrill travelled through a cloud of gloom like a death knell.
That night, an insipid performance by his team saw them succumb to modest Olympiakos 2-0, a result which left their hopes of progressing to the Champions League last-eight dangling by a thread.
Few thought there could still be fight left in this struggling side.
But, at the Theatre of Dreams on Thursday morning (Singapore time), hope sprang eternal.
Aided by a Robin van Persie hat-trick, the Red Devils fought back to clinch a 3-0 victory to overturn the tie.
Maybe, just maybe, there is a way back into the Champions League after all.
Seventh in the English Premier League standings, United are 12 points adrift of Man City in fourth, the final place that usually gains English clubs entry to Europe's premier club competition the following season.
Given that United have nine games left to play catch-up, and that City have two games in hand over them, Moyes can forget about finishing in the top four.
There is, however, another route - by winning the Champions League.
Moyes thinks they can.
After all, Liverpool and Chelsea have done that despite their teams not faring too well in the domestic league.
He said, after the win over Olympiakos: "I genuinely believe this club are capable of winning it."
Whether it was the adrenalin or the head talking, there will be no doubt that the other seven quarter-finalists, probably for the first time in Champions League history, will be hoping that they get the Red Devils in today's draw.
Such is the class of the field that United appear almost out of their depth.
Barcelona, Bayern Munich and Real Madrid form the first tier of opponents United will be desperate to avoid.
Taking down Atletico Madrid, Borussia Dortmund, Chelsea or Paris Saint-Germain, doesn't look much easier either.
To lift the cup in Lisbon in May, United must overcome three of those seven sides.
Moyes can draw comfort from a remarkable performance at Old Trafford.
To overcome a 2-0 deficit from the first leg required audacity and belief, and the Red Devils did just that.
It was encouraging to see Wayne Rooney and van Persie combining well in attack. Goalkeeper David de Gea, arguably the only player absolved of blame this term, continued with his fine form.
Ryan Giggs, the 40-year-old man, rolled back the years with a commanding midfield outing that gave the team the control that they had craved.
On an occasion when the near-impossible was demanded of them, they came through.
But there are no Olympiakos left in the competition. The seven other teams, unfortunately, simply operate on another plane. For United to win it, pigs must fly.
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